Formation of embryo sac is

Options

A. Megasporogenesis
B. Megagametogenesis
C. Microgametogenesis
D. None of the above.

Answer

To solve the question regarding the formation of the embryo sac, we can analyze the options provided:

1. **Megasporogenesis**: This is the process of forming haploid megaspores from a diploid megaspore mother cell through meiosis. While this is an important step in the overall process of embryo sac formation, it is not the final step that directly leads to the formation of the embryo sac itself.

2. **Megagametogenesis**: This is the process that follows megasporogenesis. It involves the development of the embryo sac from the functional haploid megaspore. This is the actual formation of the embryo sac that we are looking for in this question.

3. **Microgametogenesis**: This process refers to the formation of pollen grains from microspores, which is not related to the formation of the embryo sac.

Given this analysis, the correct answer to the question "Formation of embryo sac is" is **Megagametogenesis**.

### Step-by-Step Solution:
1. **Identify the processes**: Understand the definitions of megasporogenesis, megagametogenesis, and microgametogenesis.
2. **Analyze each option**:
- **Megasporogenesis**: Formation of haploid megaspores from diploid cells.
- **Megagametogenesis**: Formation of the embryo sac from a functional haploid megaspore.
- **Microgametogenesis**: Formation of pollen grains, which is unrelated to embryo sac formation.
3. **Determine the correct option**: Since the embryo sac is formed from the functional haploid megaspore, the correct process is **Megagametogenesis**.