Menstruation cycle occurs

Options

A. In all mammals
B. In eutherian animals
C. In metatherian animals
D. In all primates

Answer

**Step-by-Step Solution:**

1. **Understanding the Menstrual Cycle:**
- The menstrual cycle refers to the series of natural changes that occur in the female reproductive system, primarily involving the ovaries and the uterus. It prepares the body for potential pregnancy.

2. **Duration of the Menstrual Cycle:**
- The typical duration of the menstrual cycle is about 28 days, although it can vary from person to person.

3. **Hormonal Changes:**
- The cycle involves hormonal changes that lead to the shedding of the uterine lining if fertilization does not occur. This is a key feature of the menstrual cycle.

4. **Occurrence in Different Animals:**
- The question asks where the menstrual cycle occurs. It is important to differentiate between types of reproductive cycles in mammals.
- Most mammals do not have a menstrual cycle; instead, they have an estrous cycle.

5. **Identifying the Correct Group:**
- The menstrual cycle is specifically found in primates, which include humans, apes, and monkeys.
- Other groups such as all mammals, eutherian animals, and metatherian animals do not universally exhibit the menstrual cycle.

6. **Conclusion:**
- Therefore, the correct answer to the question "Menstruation cycle occurs" is that it occurs in **all primates**.