Question

Match List I with List II related to embryonic development at various months of pregnancy:

List I                                                     List II
A. The foetus movement starts and hair appears on the head I. 24 weeks of pregnancy
B. The foetus develops limbs and digits                    II. 20 weeks of pregnancy
C. The foetus develops external genital organs             III. 8 weeks of pregnancy
D. The foetus body is covered with fine hair; eyelids 
   separate and eyelashes are formed                       IV. 12 weeks of pregnancy

• A. A-II, B-IV, C-III, D-I
• B. A-III, B-II, C-IV, D-I
• C. A-II, B-III, C-IV, D-I
• D. A-IV, B-II, C-III, D-I

Hint:

Logic Tip: A chronological timeline helps: 8 weeks (2 months) $\rightarrow$ Limbs and digits. 12 weeks (3 months/1st trimester) $\rightarrow$ Organ systems and genitals. 20 weeks (5 months) $\rightarrow$ First movement and head hair. 24 weeks (6 months/2nd trimester) $\rightarrow$ Body hair, eyelids separate.

Answer 1

The Correct Option is C

Step 1 : Understanding the Question:
The question asks for the correct matching of human fetal developmental milestones with the specific timeline (calculated in weeks) of a standard human pregnancy. We need to associate structural formations like limbs and organs with their respective months/weeks of gestation.
Step 2 : Key Formulas and Approach:
The approach relies on the standard human embryological timeline used in clinical practice:
1. End of 2nd month (8 weeks): Major structures like limbs are established.
2. End of 1st trimester (12 weeks): Organ systems and external genitalia are developed.
3. 5th month (20 weeks): Sensations like fetal movement and head hair begin.
4. End of 2nd trimester (24 weeks): Fine hair, eyelashes, and eyelid separation occur.
Step 3 : Detailed Explanation:

Milestone A: The first detectable fetal movements (quickening) and the initial growth of hair on the fetal head are classic signs of the fifth month of development. In gestational weeks, 5 months corresponds to 20 weeks. (Match: A-II).

Milestone B: By the end of the second month of gestation, the embryo has made significant progress in defining its shape. During this period, the limbs and digits (fingers and toes) are clearly formed. 2 months equals 8 weeks. (Match: B-III).

Milestone C: By the completion of the first trimester (the first three months), the major organ systems have been formed. Specifically, the external genital organs are well-developed by this time. 3 months equals 12 weeks. (Match: C-IV).

Milestone D: At the conclusion of the second trimester (roughly 6 months), the fetus undergoes refined development. The body is covered with fine hair (lanugo), eyelashes are present, and the eyelids finally separate. 6 months equals 24 weeks. (Match: D-I).

Step 4 : Final Answer:
By aligning these developmental biological markers with the correct gestational age, we arrive at the sequence A-II, B-III, C-IV, and D-I. This matching corresponds to option (C).