Reproductive organs in humans can be categories into two categories primary and secondary . Which of the following is not a secondary sex organ ?
(a) Prostate gland (b) Mammary gland (c) seminal vesicle (d) Ovary

Options

A. Only b and d
B. Both d and c
C. Only d
D. a ,b and c

Answer

To solve the question, we need to categorize the given organs into primary and secondary sex organs.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Primary Sex Organs**: These are the organs directly involved in reproduction. In males, the primary sex organs are the testes, and in females, they are the ovaries.
- **Secondary Sex Organs**: These organs support the reproductive process but are not directly involved in gamete production. They include structures such as glands and ducts.

2. **Identify the Organs in the Question**:
- (a) Prostate gland
- (b) Mammary gland
- (c) Seminal vesicle
- (d) Ovary

3. **Analyze Each Option**:
- **Prostate Gland**: This is a male accessory gland that contributes to seminal fluid. It is not a primary sex organ.
- **Mammary Gland**: This is associated with females and is involved in milk production. It is considered a secondary sex organ.
- **Seminal Vesicle**: This is also a male accessory gland that produces a component of semen. It is not a primary sex organ.
- **Ovary**: This is the primary sex organ in females, responsible for producing ova (eggs).

4. **Determine Which is Not a Secondary Sex Organ**:
- Among the options, the ovary is the only organ that is classified as a primary sex organ. The other three (prostate gland, mammary gland, and seminal vesicle) are secondary sex organs.

5. **Conclusion**:
- The answer to the question, "Which of the following is not a secondary sex organ?" is (d) Ovary.

### Final Answer:
**(d) Ovary**