The second meiotic division of the secondary oocyte is induced by

Options

A. entry of sperms into vagina
B. entry of sperm into cytoplasm of secondary oocyte
C. after the fusion of sperm nucleus with the nucleus of secondary oocyte
D. with the entry of secondary oocyte into ampullary Isthmic zone

Answer

To solve the question regarding what induces the second meiotic division of the secondary oocyte, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Context**: The secondary oocyte is a stage in oogenesis that is arrested in metaphase II of meiosis until fertilization occurs. The completion of the second meiotic division is crucial for the formation of a mature ovum.

2. **Identifying the Trigger for Division**: The second meiotic division of the secondary oocyte is not completed until fertilization occurs. This is a key point in understanding what induces the meiotic division.

3. **Analyzing the Options**:
- **Option 1**: Entry of sperms into the vagina - This does not directly induce the meiotic division; it is merely the first step in the fertilization process.
- **Option 2**: Entry of sperms into the cytoplasm of the secondary oocyte - This is a significant event where the sperm penetrates the oocyte, leading to the initiation of the second meiotic division.
- **Option 3**: After the fusion of sperm nucleus with the nucleus of secondary oocyte - While this is an important event in fertilization, the meiotic division is triggered before this fusion occurs.
- **Option 4**: With the entry of secondary oocyte into the ampullary smooth zone - This does not directly relate to the meiotic division.

4. **Conclusion**: Based on the analysis, the correct answer is **Option 2**: the entry of sperm into the cytoplasm of the secondary oocyte induces the second meiotic division.

### Final Answer:
The second meiotic division of the secondary oocyte is induced by the entry of sperm into the cytoplasm of the secondary oocyte.

---