During the last week of the luteal phase of the menstrual cycle the following events occur.
1. A rapid drop in progesterone level takes pace.
2. Menstruation begins.
3. Lack of LH leads to the degeneration of the corpus luteum.
4. The endometrium is no longer maintained.
The correct order in which these occur is

Options

A. 1, 3, 4, 2
B. 3, 1, 4, 2
C. 1, 3, 2, 4
D. 3, 1, 2, 4

Answer

To determine the correct order of events during the last week of the luteal phase of the menstrual cycle, we can analyze the provided statements step by step.

### Step-by-Step Solution:

1. **Lack of LH leads to the degeneration of the corpus luteum.**
- At the end of the luteal phase, if there is no fertilization, the levels of Luteinizing Hormone (LH) drop. This drop causes the corpus luteum, which is responsible for producing progesterone, to degenerate.

2. **A rapid drop in progesterone level takes place.**
- As the corpus luteum degenerates, it can no longer produce progesterone. This leads to a rapid decrease in progesterone levels in the body.

3. **The endometrium is no longer maintained.**
- Progesterone is crucial for maintaining the endometrium (the lining of the uterus). With the drop in progesterone levels, the endometrium cannot be sustained and begins to break down.

4. **Menstruation begins.**
- As the endometrium breaks down, it leads to the shedding of the uterine lining, which is what we recognize as menstruation. This marks the beginning of the menstrual phase.

### Correct Order of Events:
1. Lack of LH leads to the degeneration of the corpus luteum.
2. A rapid drop in progesterone level takes place.
3. The endometrium is no longer maintained.
4. Menstruation begins.