From the following, select the process which take place during the development of embryo sac.
(a.) Functional megaspore divides by three mitotic divisions.
(b.) Type of nuclear division is free , where no cell wall formation takes place.
(c.) Among eight nuclei. Six are surrounded by a cell wall.
(d.) Central cell is situated below the egg apparatus .

Options

A. a and b
B. b and d
C. c and d
D. All are correct

Answer

To solve the question regarding the processes that take place during the development of the embryo sac, we will analyze each of the given statements step by step.

### Step 1: Analyze Statement (a)
**Statement (a):** Functional megaspore divides by three mitotic divisions.

- The functional megaspore is the only megaspore that survives after meiosis. It undergoes three rounds of mitotic division.
- This results in the formation of a total of eight nuclei, which will later be organized into cells.

**Conclusion:** This statement is correct.

### Step 2: Analyze Statement (b)
**Statement (b):** Type of nuclear division is free, where no cell wall formation takes place.

- During the initial divisions of the functional megaspore, the nuclei divide without the formation of cell walls between them.
- This is known as free nuclear division, and it continues until the final arrangement of the nuclei into cells occurs.

**Conclusion:** This statement is correct.

### Step 3: Analyze Statement (c)
**Statement (c):** Among eight nuclei, six are surrounded by a cell wall.

- After the three mitotic divisions, the eight nuclei are organized into seven cells.
- Out of these, six nuclei are indeed surrounded by cell walls, forming three antipodal cells, two synergids, and one egg cell. The remaining two nuclei (the polar nuclei) in the central cell do not have cell walls surrounding them.

**Conclusion:** This statement is correct.

### Step 4: Analyze Statement (d)
**Statement (d):** Central cell is situated below the egg apparatus.

- In the typical orientation of the embryo sac, the egg apparatus (which includes the egg cell and synergids) is located at the micropylar end, while the central cell is located towards the chalazal end.
- Therefore, the central cell is not below the egg apparatus; it is actually above it in the typical orientation.

**Conclusion:** This statement is incorrect.

### Final Conclusion
Based on the analysis of each statement:
- Statements (a), (b), and (c) are correct.
- Statement (d) is incorrect.

Thus, the correct answer to the question is that statements (a), (b), and (c) are true regarding the development of the embryo sac, while statement (d) is false.