Which is correct ?

Options

A. Menstrual cycle is present in all mammals
B. Menstrual cycle is present in all primates
C. Estrous cycle occurs in all mammals
D. Most mammals are ovoviviparous

Answer

To determine which statement is correct, let's analyze each one step by step.

### Step 1: Analyze the first statement
**Statement 1:** The menstrual cycle is present in mammals.

- The menstrual cycle is not present in all mammals. It is primarily observed in primates, including humans, apes, and monkeys. Other mammals typically exhibit an estrous cycle instead. Therefore, this statement is **incorrect**.

### Step 2: Analyze the second statement
**Statement 2:** The menstrual cycle is present in primates.

- This statement is accurate. The menstrual cycle is indeed present in primates, which include humans, monkeys, and apes. Thus, this statement is **correct**.

### Step 3: Analyze the third statement
**Statement 3:** The estrous cycle occurs in all mammals.

- This statement is also incorrect. While many mammals do have an estrous cycle, it does not occur in all mammals. For example, primates have a menstrual cycle instead. Therefore, this statement is **incorrect**.

### Step 4: Analyze the fourth statement
**Statement 4:** Most mammals are oviparous.

- This statement is incorrect. Most mammals are viviparous, meaning they give birth to live young. Oviparous mammals, such as monotremes (like the platypus), are a small minority. Therefore, this statement is **incorrect**.

### Conclusion
After analyzing all the statements, the only correct statement is:

**The menstrual cycle is present in primates.**