Which event does not occur if fertilization not occur in menstrual cycle.

Options

A. (a) Progesterone is decreased after 22nd day.
B. (b) Corpus luteum degenerates.
C. (c) Degeneration and shedding of endometrium.
D. (d)Degeneration of ovary

Answer

### Step-by-Step Solution:

1. **Understanding the Menstrual Cycle**: The menstrual cycle involves several hormonal changes that prepare the female body for potential pregnancy. Key hormones involved include estrogen and progesterone.

2. **Identifying the Role of Fertilization**: Fertilization is the process where a sperm cell fertilizes an ovum (egg cell), leading to the formation of a zygote. If fertilization does not occur, certain events in the menstrual cycle will take place.

3. **Effects of No Fertilization**:
- **Decrease in Progesterone**: If fertilization does not occur, the corpus luteum (which produces progesterone) will degenerate, leading to a decrease in progesterone levels. This hormone is crucial for maintaining the uterine lining for a potential pregnancy.
- **Degeneration of Corpus Luteum**: The corpus luteum will break down if there is no fertilization, which is a normal part of the cycle.
- **Degeneration and Shedding of Endometrium**: The endometrial lining, which thickens in preparation for implantation, will shed if there is no embryo to implant, resulting in menstruation.

4. **Identifying the Odd Event**: The question asks for the event that does not occur if fertilization does not take place.
- **D) Degeneration of Ovary**: The ovaries do not degenerate if fertilization does not occur. They continue to function and produce ova (eggs) for future cycles.

5. **Conclusion**: The correct answer is D) degeneration of ovary, as this event does not occur when fertilization does not take place.

### Final Answer:
**D) Degeneration of Ovary**

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