Acrosomal reaction occurs at the time of

Options

A. Excretion
B. Painful stimulation
C. Movement of sperm
D. Fertilisation.

Answer

**Step-by-Step Solution:**

1. **Understanding the Acrosomal Reaction**: The acrosomal reaction is a crucial event that occurs when a sperm cell encounters an egg (oocyte). This reaction involves the release of enzymes from the acrosome, which is a cap-like structure on the head of the sperm.

2. **Identifying the Context**: The acrosomal reaction is specifically important during the process of fertilization. It helps the sperm penetrate the protective layers surrounding the egg, allowing for the fusion of the sperm and egg membranes.

3. **Locating the Site of Fertilization**: The fertilization typically occurs in the ampulla of the fallopian tube, where the sperm meets the secondary oocyte.

4. **Conclusion**: Given that the acrosomal reaction facilitates the sperm's ability to penetrate the egg during fertilization, we can conclude that the acrosomal reaction occurs at the time of fertilization.

5. **Final Answer**: Therefore, the correct answer to the question is **D, fertilization**.

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