Which of the following event is preceded by formation of embryo-sac?

Options

A. Division of megaspore mother cell by mitosis
B. Endosperm formation
C. division of megaspore mother cell by meiosis
D. Formation of female gamete

Answer

To solve the question "Which of the following event is preceded by formation of embryo-sac?", we will analyze the options step by step.

### Step 1: Understand the Concept of Embryo-Sac Formation
The embryo-sac is the female gametophyte in flowering plants, which develops from the megaspore after it undergoes meiosis. The formation of the embryo-sac is a crucial step in the reproductive cycle of angiosperms.

**Hint:** Remember that the embryo-sac is formed from the megaspore after meiosis, not mitosis.

### Step 2: Analyze the Options
1. **Division of megaspore mother cell by mitosis**: This option is incorrect because the megaspore mother cell undergoes meiosis to produce megaspores, which then develop into the embryo-sac.

**Hint:** Mitosis is not involved in the initial formation of the embryo-sac.

2. **Endosperm formation**: This occurs after fertilization, where the fertilized ovule develops into a seed and the surrounding tissue becomes the endosperm. Thus, this option is also incorrect.

**Hint:** Endosperm formation happens after fertilization, which follows embryo-sac formation.

3. **Division of megaspore mother cell by meiosis**: This option is correct because the megaspore mother cell divides by meiosis to produce four megaspores, of which typically one survives to develop into the embryo-sac.

**Hint:** Meiosis is the key process that leads to the formation of the embryo-sac.

4. **Formation of female gamete**: This is also incorrect in the context of the question because the female gamete (egg) is formed as part of the embryo-sac development, not before it.

**Hint:** The female gamete is a product of the embryo-sac, not a precursor.

### Step 3: Conclusion
After analyzing all the options, the correct answer is the third option: **Division of megaspore mother cell by meiosis**. This event directly precedes the formation of the embryo-sac.

**Final Answer:** The event that is preceded by the formation of the embryo-sac is the **division of megaspore mother cell by meiosis**.