Comprehension

The theory of plate tectonics describes the motions of the lithosphere, the comparatively rigid outer layer of the Earth that includes all the crust and part of the underlying mantle. The lithosphere is divided into a few dozen plates of various sizes and shapes; in general the plates are in motion with respect to one another. A mid-ocean ridge is a boundary between plates where new lithospheric material is injected from below. As the plates diverge from a mid-ocean ridge they slide on a more yielding layer at the base of the lithosphere.

Since the size of the Earth is essentially constant, new lithosphere can be created at the mid-ocean ridges only if an equal amount of lithospheric material is consumed elsewhere. The site of this destruction is another kind of plate boundary: a subduction zone. There one plate dives under the edge of another and is reincorporated into the mantle. Both kinds of plate boundary are associated with fault systems, earthquakes and volcanism, but the kinds of geologic activity observed at the two boundaries are quite different.

The idea of sea-floor spreading actually preceded the theory of plate tectonics. In its original version, in the early 1960s, it described the creation and destruction of the ocean floor, but it did not specify rigid lithospheric plates. The hypothesis was substantiated soon afterward by the discovery that periodic reversals of the Earth's magnetic field are recorded in the oceanic crust. As magma rises under the mid-ocean ridge ferromagnetic minerals in the magma become magnetized in the direction of the geomagnetic field. When the magma cooks and solidifies, the direction and the polarity of the field are preserved in the magnetized volcanic rock. Reversals of the field give rise to a series of magnetic stripes running parallel to the axis of the rift. The oceanic crust thus serves as a magnetic tape recording of the history of the geomagnetic field that can be dated independently. The width of the stripes indicates the rate of the sea-floor spreading.

Question: 1

What is the core theme of the passage?

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Look at what the first sentence introduces and check whether every paragraph keeps building on that same idea.
Updated On: Jul 21, 2026
  • Magnetic field reversal
  • The formation of magma
  • The location of mid-ocean ridges
  • Plate tectonic theory
Show Solution

The Correct Option is D

Solution and Explanation

Step 1: Understanding the Question:
We need to find the single idea that best covers everything the passage talks about, from the first line to the last.

Step 2: Key Formula or Approach:
For a core theme question, check what the opening sentence introduces and then see if every paragraph keeps returning to that same idea. If yes, that idea is the theme. If a paragraph only mentions something once and moves on, that something is a supporting detail, not the theme.

Step 3: Detailed Explanation:
The passage opens with "The theory of plate tectonics describes the motions of the lithosphere."
The second paragraph explains how lithosphere is destroyed at subduction zones, which is still part of plate tectonic theory.
The third paragraph brings in sea floor spreading and the magnetic stripe evidence, both offered as proof that strengthens plate tectonic theory.
Magnetic field reversal, magma formation, and mid-ocean ridge location are each used only as supporting facts inside this larger explanation, not as the passage's main subject.

Step 4: Final Answer:
Since every paragraph circles back to explaining and supporting plate tectonic theory, that is the core theme. This is option (d).
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Question: 2

Which of the following can be created at mid-ocean ridges?

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Reread the sentence describing what happens at a mid-ocean ridge, and note what gets created or injected there.
Updated On: Jul 21, 2026
  • Subduction zone
  • Lithosphere
  • Fault systems
  • Geomagnetic field
Show Solution

The Correct Option is B

Solution and Explanation

Step 1: Understanding the Question:
We must identify which item the passage says is formed at a mid-ocean ridge.

Step 2: Key Formula or Approach:
Look for the sentence in the passage that pairs mid-ocean ridge with a verb like created or injected, and match its object to the options.

Step 3: Detailed Explanation:
The passage says, "A mid-ocean ridge is a boundary between plates where new lithospheric material is injected from below."
It also says, "new lithosphere can be created at the mid-ocean ridges only if an equal amount of lithospheric material is consumed elsewhere."
Both sentences point to the same object, lithosphere, being created at the ridge.
Subduction zones, by contrast, are where lithosphere is destroyed, which rules out option (a).
Fault systems and the geomagnetic field are mentioned elsewhere in different contexts, not as things produced at ridges.

Step 4: Final Answer:
Lithosphere is created at mid-ocean ridges, so the answer is option (b).
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Question: 3

Which of the following is true about tectonic plates?

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Check the first paragraph's exact description of how the plates behave with respect to each other.
Updated On: Jul 21, 2026
  • They move in relationship to one another
  • They have unchanging borders
  • They are located far beneath the lithosphere
  • They have the same shape
Show Solution

The Correct Option is A

Solution and Explanation

Step 1: Understanding the Question:
We are asked to pick the one true statement about tectonic plates as described in the passage.

Step 2: Key Formula or Approach:
Check each option against the exact wording used for plates in paragraph one, since that is where plates are first described.

Step 3: Detailed Explanation:
The passage says plates are "of various sizes and shapes," which rules out option (d), same shape.
It says "in general the plates are in motion with respect to one another," which rules out option (b), unchanging borders, since motion means the borders keep shifting.
Plates are pieces of the lithosphere, not something beneath it, so option (c) is wrong.
Global warming is never mentioned in the passage, so option (e) has no support at all.
The remaining option, that plates move in relationship to one another, matches the passage's own words exactly.

Step 4: Final Answer:
Tectonic plates move with respect to one another, so the answer is option (a).
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Question: 4

According to the passage, which of the following statements about the lithosphere is least likely to be true?

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Compare each option to the passage's own definition of the lithosphere; one option mentions something never stated in the text.
Updated On: Jul 21, 2026
  • It is a relatively inflexible layer of the Earth
  • It includes the crust and some of the mantle of the Earth
  • It is made up entirely of volcanic ash
  • It is divided into plates of various shapes and sizes
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Understanding the Question:
This is a reverse question, we need the option that the passage does not back up, not the one it confirms.

Step 2: Key Formula or Approach:
Match each option to the passage's own definition of the lithosphere and eliminate every option that has direct textual support. Whatever is left, and unsupported, is the answer.

Step 3: Detailed Explanation:
"Comparatively rigid outer layer" supports option (a), inflexible.
"Includes all the crust and part of the underlying mantle" supports option (b).
"Divided into a few dozen plates of various sizes and shapes" supports option (d).
No sentence anywhere in the passage mentions volcanic ash, and the actual composition given is crust and mantle rock, not ash.

Step 4: Final Answer:
Option (c), "It is made up entirely of volcanic ash," is the one without support, so it is the least likely to be true.
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Question: 5

What does the author imply about the periodic reversal of the Earth's magnetic field?

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Find the sentence right after periodic reversals is introduced and note which hypothesis it is said to substantiate.
Updated On: Jul 21, 2026
  • It analyses the association of plate boundaries
  • It indicates the amount of magma present in earth's crust
  • It clarifies formation of new lithosphere
  • It supports the hypothesis of sea-floor spreading
Show Solution

The Correct Option is D

Solution and Explanation

Step 1: Understanding the Question:
We need to find what role the periodic reversal of the magnetic field plays according to the author's argument.

Step 2: Key Formula or Approach:
Find the sentence that directly follows the mention of periodic reversals and see what claim it is used to back up.

Step 3: Detailed Explanation:
The passage reads, "The idea of sea-floor spreading actually preceded the theory of plate tectonics... The hypothesis was substantiated soon afterward by the discovery that periodic reversals of the Earth's magnetic field are recorded in the oceanic crust."
Here "the hypothesis" refers to sea floor spreading, and "substantiated" means proved or supported.
So the magnetic reversal discovery is presented as evidence that confirms the sea floor spreading idea, not as evidence about magma quantity, lithosphere formation, or plate boundary comparisons.

Step 4: Final Answer:
The periodic reversal supports the hypothesis of sea-floor spreading, so the answer is option (d).
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Question: 6

The author states that the width of the stripes preserved in magnetized volcanic rock give information about the

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The very last sentence of the passage answers this directly.
Updated On: Jul 21, 2026
  • Date of a volcanic eruption
  • Speed of sea-floor spreading
  • Width of oceanic crust
  • Future behavior of the geomagnetic field
Show Solution

The Correct Option is B

Solution and Explanation

Step 1: Understanding the Question:
We need the exact fact the author connects to the width of the magnetic stripes in volcanic rock.

Step 2: Key Formula or Approach:
The final sentence of a descriptive passage often carries a specific, testable fact. Read it literally and match it word for word against the options.

Step 3: Detailed Explanation:
The last sentence of the passage says, "The width of the stripes indicates the rate of the sea-floor spreading."
"Rate" is simply another word for "speed," so this maps directly onto option (b).
Dating, crust width, future field behavior, and lava temperature are separate facts mentioned or implied elsewhere, none of which the passage attaches to stripe width.

Step 4: Final Answer:
Stripe width tells us the speed of sea-floor spreading, so the answer is option (b).
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Question: 7

Since the size of the Earth is essentially constant, new lithosphere can be created at the mid-ocean ridges only when

Show Hint

Look for the "only if" condition attached to the sentence about the Earth's constant size.
Updated On: Jul 21, 2026
  • Magma rises from earth's crust
  • Polarity of magnetic field is maintained
  • Tectonic plates are incorporated into the mantle
  • An equal amount of lithospheric material is consumed elsewhere
Show Solution

The Correct Option is D

Solution and Explanation

Step 1: Understanding the Question:
We need the exact "only if" condition the passage gives for new lithosphere to be created at mid-ocean ridges.

Step 2: Key Formula or Approach:
When a passage uses the phrase "only if," the condition that follows it is usually the direct answer to a question built around that same sentence.

Step 3: Detailed Explanation:
The passage says, "Since the size of the Earth is essentially constant, new lithosphere can be created at the mid-ocean ridges only if an equal amount of lithospheric material is consumed elsewhere."
The reasoning is simple, if the Earth stayed the same size while lithosphere kept being added at ridges, the planet would have to grow. Since it does not grow, something else must destroy an equal amount of lithosphere, which the passage later identifies as the subduction zone.
Magma rising, magnetic polarity, and plates being incorporated into the mantle are all facts mentioned in the passage, but they are not the specific balancing condition this sentence describes.

Step 4: Final Answer:
New lithosphere is created at ridges only when an equal amount of lithospheric material is consumed elsewhere, so this option is correct.
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Question: 8

Which of the following serve(s) as a magnetic tape recording of the history of the geomagnetic field?

Show Hint

Find where the passage uses the phrase magnetic tape recording and see which noun it is describing.
Updated On: Jul 21, 2026
  • Tectonic plates
  • Oceanic crust
  • Ferromagnetic minerals
  • Geomagnetic field
Show Solution

The Correct Option is B

Solution and Explanation

Step 1: Understanding the Question:
We must identify what the passage names as the "magnetic tape recording" of the geomagnetic field's history.

Step 2: Key Formula or Approach:
Find the sentence using the phrase "magnetic tape recording" and read exactly what noun it is describing.

Step 3: Detailed Explanation:
The passage says, "The oceanic crust thus serves as a magnetic tape recording of the history of the geomagnetic field that can be dated independently."
The subject of this sentence is "the oceanic crust," which is described as the recording itself.
The geomagnetic field is what gets recorded, not the recording medium, which rules out option (d).
Ferromagnetic minerals are only the tiny particles inside the crust that align with the field, they are part of the mechanism, but the passage credits the crust as a whole with acting as the tape.
Tectonic plates are never linked to magnetic recording anywhere in the passage.

Step 4: Final Answer:
The oceanic crust is the magnetic tape recording of the geomagnetic field's history, so the answer is option (b).
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Top Questions on Reading Comprehension

Questions Asked in IBSAT exam

Although cynics may like to see the government’s policy for women in terms of the party’s internal power struggles, it will nevertheless be churlish to deny that it represents a pioneering effort aimed at bringing about sweeping social reforms. In its language, scope and strategies, the policy document displays a degree of understanding of women’s needs that is uncommon in government pronouncements. This is due in large part to the participatory process that marked its formulation, seeking the active involvement right from the start of women’s groups, academic institutions and non-government organizations with grass roots experience.
The result is not just a lofty declaration of principles but a blueprint for a practical programme of action. The policy delineates a series of concrete measures to accord women a decision-making role in the political domain and greater control over their economic status. Of especially far-reaching impact are the devolution of control of economic infrastructure to women, notably at the gram panchayat level, and the amendments proposed in the Hindu Succession Act of 1956 to give women coparcenary rights.
 An enlightened aspect of the policy is its recognition that actual change in the status of women cannot be brought about by the mere enactment of socially progressive legislation. Accordingly, it focuses on reorienting development programmes and sensitizing administrations to address specific situations as, for instance, the growing number of households headed by women, which is a consequence of rural-urban migration. The proposal to create an equal-opportunity police force and give women greater control of police stations is an acknowledgement of the biases and callousness displayed by the generally all-male lawenforcement authorities in cases of dowry and domestic violence. While the mere enunciation of such a policy has the salutary effect of sensitizing the administration as a whole, it does not make the task of its implementation any easier. 
This is because the changes it envisages in the political and economic status of women strike at the root of power structures in society and the basis of man woman relationships. There is also the danger that reservation for women in public life, while necessary for their greater visibility, could lapse into tokenism or become a tool in the hands of vote seeking politicians. Much will depend on the dissemination of the policy and the ability of elected representatives and government agencies to reorder their priorities.
  • IBSAT
  • Reading Comprehension
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Generally, people experience stress in their day-to-day lives, but more than thirty million Americans suffer from something more intense than that. Anxiety disorders are the second-most-common mental health problem in the country, and they can be paralyzing. Sometimes, day-to-day stress and anxiety are hard to tell apart, but the easiest way to distinguish them is that stress is brought on by actual events, and then dissipates, whereas anxiety is a more pervasive worry, that often attaches itself to specific areas of your life, like your relationship, job or health, says psychologist Terry Mooney.
This anxiety does not dissipate, and in fact, it can increase to the level where it begins to change your behavior. That’s when it’s characterized as an anxiety disorder. Anxiety can keep you safe, helping you recognize danger, and cope with it, says Mooney. But if you begin to see danger lurking around every corner, or worry over and over again about the same events, then you might be dealing with something more substantial, like an anxiety disorder. 
People with anxiety disorders often begin to avoid activities or circumstances that make them anxious, said John Forsyth, associate professor of Psychology at the State University of New York at Albany and director of the Anxiety Disorders Research Programme at the university. People may stop driving, or stop going to parties. They may stop travelling or even avoid leaving the house. It’s this curtailing of activities that causes the suffering, Forsyth said, making you feel that ‘life is shrinking around you.’
 Anxiety disorders come in a variety of forms and manifest themselves in different ways. Generalized anxiety disorder is characterized by ongoing worry about everyday tasks, even when there is no clear reason to worry. People with social anxiety disorder experience intense worry over social interactions, and often feel judged by people or worry that they will embarrass themselves. Post-traumatic stress disorder, which is characterized by people re-living a frightening event over and over again, is also considered an anxiety disorder. Obsessive-compulsive disorder is when people take on obsessive rituals that help them maintain the illusion of control. Often repetitive in nature, obsessive compulsive rituals can include cleaning, checking and rechecking something, counting or endlessly reviewing conversations in their mind. Treatment is available for anxiety disorders. People can use a variety of approaches, including therapy, medication and exercise.
  • IBSAT
  • Reading Comprehension
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I am the family face; flesh perishes. I live on, projecting trait and trace through time to times anon, and leaping from place to place over oblivion.
So wrote Thomas Hardy in his poem, Heredity, describing direct descent of life from one generation to the next. Indeed, the poem reflects the DNA in our genome. Dr.Drew Endy of MIT quoted this when he described how people at the J. Craig Venter Institute (JCVI) bypass nature’s constraint of direct descent. Scientists there have used chemistry and biochemistry to produce the first synthetic genome in the laboratory. They chemically synthesized many fragments of the DNA, encoding the 582,970-units-long genome of a bacterium called Mycoplasma genitalium. Next, they assembled these fragments in perfect order to generate the genome of the bacterium.
The DNA sequence of the synthetic one was confirmed to be identical to the natural one. While the DNA pieces were synthesized chemically, the stitching together was done using the biochemical machinery of a host cell. About 100 pieces of the genome, each 5000-7000 units long in DNA sequence, were first joined to produce 25 sub-assemblies, each about 24000 base pairs long. These were then introduced into the bacterium E. coli to produce sufficient DNA for the next steps. Next, they repeated the procedure to generate large fragments comprising l/4th of the whole genome of M.genitalium.
Now, they used the clever trick of exploiting the process called homologous recombination. This is a basic essential process in every cell, which physically rearranges the two strands of DN The JCVI researchers inserted the synthesized DNA fragments into yeast and utilized its homologous recombination ability to generate the whole 580,000 long genome of M.genitalium in one step. 
This is clearly a landmark work that leads into the brave new world of synthesizing life itself in the laboratory. It was hardly 200 years ago when Friedrich Wohler synthesized urea, an organic molecule, in the chemical laboratory, thus throwing out the notion of ‘vital forces’ involved in the components of living organisms. What is the next step, making life itself in the lab, bypassing nature? With single cell organisms like M.genitalium, it might not be far away. It is now possible in the lab to do so, by inserting the genome into a ‘host’ cell and asking the latter to make the bacterium of your choice. If only we find a way to insert the bacterial genome into this proto-cell, and somehow trigger it to make the bacterium itself! We would have chemically created life in the la This is not a pipedream; JCVI scientists are already on the job, and my bet is they will do it within a few years. 
This surely raises ethical questions, a matter that JCVI is keenly aware of and is already engaged in with ethicists. Even their present work on M.genitalium was done with prior approval of ethical experts. But then, today it is M.genitalium, tomorrow it could be a more advanced, multi-cellular organism, and that could flummox even the ethicist. Assisted reproduction, which is the other side of the coin and truly a recently initiated technology, has become ethically and morally acceptable. Cloning of Dolly, the sheep, has not raised any outrage, but cloning a human certainly does.
  • IBSAT
  • Reading Comprehension
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