In a average menstrual cycle of 28 days , which of these events is correctly matched with the time of its occurrence ?

Options

A. Release of ovum : `5^(th)` day
B. Endometrium degenerates : `5^(th) -10^(th)` day
C. Endometrium secretes nutrients for implantation : `15^(th)-28^(th)` day
D. Rise in progesterone level : `1^(st) -15^(th)` day

Answer

To solve the question regarding the events of an average menstrual cycle of 28 days, we need to analyze each option provided and match it with the correct timing of occurrence. Here’s a step-by-step breakdown:

### Step 1: Understand the Phases of the Menstrual Cycle
The menstrual cycle can be divided into several phases:
- **Menstrual Phase**: Days 1-5 (bleeding occurs)
- **Follicular Phase**: Days 6-14 (endometrium starts to rebuild)
- **Ovulation**: Around Day 14 (release of ovum)
- **Luteal Phase**: Days 15-28 (preparation for potential implantation)

### Step 2: Analyze Each Option
1. **Release of ovum on the 5th day**:
- Incorrect. Ovulation occurs around Day 14, not Day 5.

2. **Endometrium degenerates 5th to 10th day**:
- Correct. After menstruation, the endometrium begins to break down as the cycle progresses towards ovulation.

3. **Endometrium secretes nutrients for implantation from 15th to 28th day**:
- Incorrect. The endometrium does prepare for implantation during the luteal phase, but it does not specifically secrete nutrients in that manner.

4. **Rise in progesterone level from 1st to 15th day**:
- Incorrect. Progesterone levels rise after ovulation, primarily during the luteal phase (Days 15-28).

### Step 3: Conclusion
The only correctly matched event with its occurrence in the menstrual cycle is:
- **Endometrium degenerates from 5th to 10th day**.

### Final Answer
The correct option is: **Endometrium degenerates 5th to 10th day**.

---