Which of the following cell of embryo sac is first haploid, later diploid and finally becomes triploid?

Options

A. antepodal
B. synergids
C. secondary nucleus
D. central cell

Answer

To solve the question regarding which cell of the embryo sac is first haploid, later diploid, and finally becomes triploid, we will analyze the different cells present in the embryo sac and their ploidy levels during the fertilization process.

### Step-by-Step Solution:

1. **Understanding the Embryo Sac**:
The embryo sac is a structure found in the ovule of flowering plants. It contains several cells, each with different roles in the process of fertilization.

2. **Identifying the Cells**:
The main cells in the embryo sac include:
- Antipodal cells
- Synergids
- Egg cell
- Central cell (which contains two polar nuclei)

3. **Ploidy Levels of Each Cell**:
- **Antipodal Cells**: These are haploid (n) cells that are located at the opposite end of the embryo sac from the micropyle.
- **Synergids**: These are also haploid (n) cells located at the micropyle end of the embryo sac.
- **Egg Cell**: This is a haploid (n) cell that, when fertilized by a sperm cell, becomes diploid (2n).
- **Central Cell**: This cell is unique as it contains two polar nuclei and is haploid (n) before fertilization. When fertilized by a second sperm cell, it becomes triploid (3n).

4. **Analyzing the Question**:
The question asks for a cell that is first haploid, then diploid, and finally becomes triploid.
- The **egg cell** fits this description as it starts as haploid (n), becomes diploid (2n) upon fertilization with one sperm cell, and the **central cell** becomes triploid (3n) when fertilized by a second sperm cell.

5. **Conclusion**:
The correct answer to the question is the **central cell** of the embryo sac, as it is the one that transitions from haploid to diploid and finally to triploid.

### Final Answer:
The cell of the embryo sac that is first haploid, later diploid, and finally becomes triploid is the **central cell**.