Select the correct Statement :

Options

A. The first movements of foetus and appearance of hairs on the head are usually observed during sixth month of pregnancy.
B. The mammary glands of the female undergo differentiation before puberty and start producing milk at the end of pregnancy.
C. Trophoblast cells contain specialised stem cells which have the potency to give rise all the tissue and organs.
D. After implantation , finger-like projection appears on the trophoblast which is surrounded by uterine tissue and meternal blood.

Answer

To solve the question, we need to analyze each statement provided and determine which one is correct based on our knowledge of human embryology and pregnancy.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "The first movement of the fetus and appearance of hair on the head are usually observed during 6 months of the pregnancy."
- **Evaluation**: The first fetal movements (quickening) are typically felt around 18-20 weeks (approximately 4.5 to 5 months), not 6 months. Hair on the head also starts to appear around this time, but the statement is misleading as it suggests both occur at 6 months. Hence, this statement is incorrect.

2. **Statement 2**: "The mammary glands of the female undergo differentiation before puberty and they start producing milk at the end of the pregnancy."
- **Evaluation**: Mammary glands do undergo some development before puberty, but they do not start producing milk until after parturition (birth). Therefore, this statement is also incorrect.

3. **Statement 3**: "The trophoblast cells contain specialized stem cells which have the potency to give rise to the tissue and organs."
- **Evaluation**: Trophoblast cells are involved in implantation and form part of the placenta, but they do not contain stem cells that give rise to tissues and organs. The inner cell mass of the blastocyst contains the pluripotent stem cells. Thus, this statement is incorrect.

4. **Statement 4**: "After implantation, finger-like projections appear on the trophoblast which is surrounded by the uterine tissue and the maternal blood."
- **Evaluation**: This statement is correct. After implantation, the trophoblast cells differentiate and form projections called chorionic villi, which invade the uterine tissue and establish a connection with maternal blood, forming the placenta.

### Conclusion:
The correct statement is **Statement 4**.