| 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 |
Solution
Core Logic
According to the human embryonic development timeline:
- By the end of the second month (8 weeks), the foetus develops limbs and digits (B-III).
- By the end of 12 weeks (first trimester), most major organ systems are formed, including well-developed external genital organs (C-IV).
- During the fifth month (approx. 20 weeks), the first movements of the foetus and appearance of hair on the head are observed (A-II).
- By the end of 24 weeks (second trimester), the body is covered with fine hair, eyelids separate, and eyelashes are formed (D-I).
Step 1: Final Conclusion
The correct matches are A-II, B-III, C-IV, D-I.
Pattern Recognition
Movement & head hair = 5th month / 20 weeks (A-II). Limbs & digits = end of 2nd month / 8 weeks (B-III). Match these two and the correct option is clear.
Chapter Mix
Class 12 Biology: Human Reproduction