Spot the odd one out from the following structures with reference to the male reproductive system.

Options

A. Rete testis
B. Epididymis
C. Vasa efferentia
D. Isthmus

Explanation

To solve the question of spotting the odd one out from the given structures related to the male reproductive system, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structures**: First, we need to look at the structures mentioned in the options. The options are:
- A: Retrotestes
- B: Epididymis
- C: Vas Afferentia (or Vas Afferents)
- D: Isthmus

2. **Analyze Each Structure**:
- **Retrotestes**: This is a network of tubules located in the male reproductive system that is involved in the transport of sperm.
- **Epididymis**: This is a tubular structure where sperm mature and are stored, clearly part of the male reproductive system.
- **Vas Afferentia**: These are ducts that carry sperm from the testis to the epididymis, also part of the male reproductive system.
- **Isthmus**: This structure is part of the female reproductive system, specifically a section of the fallopian tubes.

3. **Determine the Odd One Out**: After analyzing each structure, we can see that:
- The first three options (Retrotestes, Epididymis, Vas Afferentia) are all components of the male reproductive system.
- The last option (Isthmus) is a component of the female reproductive system.

4. **Conclusion**: Therefore, the odd one out is **D: Isthmus**.

### Final Answer:
The odd one out is **D: Isthmus**.

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