Question:medium

Given below are two statements :
Statement I: In polluted water values of both dissolved oxygen and BOD are very low.
Statement II: Eutrophication results in decrease in the amount of dissolved oxygen.
In the light of the above statements, choose the most appropriate answer from the options given below :

Updated On: Mar 23, 2026
  • Both Statement I and Statement II are true.
  • Both Statement I and Statement II are false.
  • Statement I is true but Statement II is false.
  • Statement I is false but Statement II is true.
Show Solution

The Correct Option is D

Solution and Explanation

To evaluate the given statements, let's delve into the concepts of dissolved oxygen (DO), biochemical oxygen demand (BOD), and eutrophication in water bodies:

  1.  Statement I Analysis:
    • Dissolved Oxygen (DO): It indicates the amount of oxygen available in water, essential for aquatic life. In clean water, the DO is high.
    • Biochemical Oxygen Demand (BOD): It measures the amount of oxygen required by aerobic microorganisms to decompose organic material in water. Higher BOD indicates more organic pollutants in water.
    • Poor water quality or polluted water usually has high BOD and low DO. Thus, Statement I ("In polluted water values of both dissolved oxygen and BOD are very low") is factually incorrect. Polluted water would typically have high BOD because of the abundant organic matter and low DO due to the oxygen consumption by microorganisms.
  2. Statement II Analysis:
    • Eutrophication: This is a process where a water body becomes overly enriched with nutrients, leading to excessive growth of algae and plant life.
    • The growth of algae can block sunlight and reduce oxygen levels in water as the algae decompose, leading to hypoxic conditions. This results in a decrease in the amount of dissolved oxygen in the water.
    • Therefore, Statement II ("Eutrophication results in decrease in the amount of dissolved oxygen") is correct.

In conclusion, considering the analysis above:

  • Statement I is false but Statement II is true.

Therefore, the correct answer is:

Statement I is false but Statement II is true.

 

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