Embryo sac occurs in

Options

A. embryo
B. axis part of embryo
C. ovule
D. endosperm

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where the embryo sac occurs. We need to identify the correct structure among the given options: embryo, axis part of embryo, ovule, and endosperm.

2. **Identifying the Correct Structure**: The embryo sac is a crucial part of the plant reproductive system. It is specifically formed within the ovule.

3. **Process of Formation**: The embryo sac is formed through two main processes:
- **Megasporogenesis**: This is the process where the megaspore mother cell (MMC), which is diploid, undergoes meiosis to produce four haploid megaspores.
- **Megagametogenesis**: Out of the four megaspores formed, three degenerate, and one survives to become the functional megaspore. This functional megaspore develops into the embryo sac.

4. **Structure of the Embryo Sac**: The functional megaspore undergoes three mitotic divisions without cytokinesis, resulting in eight nuclei. These nuclei organize into a structure known as the embryo sac, which consists of seven cells and eight nuclei.

5. **Conclusion**: Based on the above information, we conclude that the embryo sac occurs in the ovule. Therefore, the correct answer is option 3: ovule.

---