Which statement regarding Nereis is wrong?

Options

A. It has nephridium for excretion
B. It is metamerically segmented.
C. It is monoecious,
D. It has parapodia for swimming

Answer

To determine which statement regarding Nereis is wrong, we can analyze each of the provided statements one by one:

1. **Nereis has nephridia for excretion.**
- Nereis, which belongs to the phylum Annelida, does indeed possess nephridia. Nephridia are excretory organs that help in the removal of waste products from the body. Therefore, this statement is **correct**.

2. **Nereis is metamerically segmented.**
- Nereis exhibits metameric segmentation, meaning its body is divided into a series of segments (metameres). Each segment contains similar sets of organs and structures. Thus, this statement is also **correct**.

3. **Nereis is monoceious.**
- The term "monoceious" refers to organisms that have both male and female reproductive organs in the same individual. However, Nereis is actually dioecious, meaning it has separate male and female individuals. Therefore, this statement is **wrong**.

4. **Nereis has parapodia for swimming.**
- Parapodia are paired appendages found in Nereis that assist in locomotion and swimming. This statement is **correct**.

Based on the analysis, the wrong statement regarding Nereis is that it is monoceious.

### Summary of the Solution:
- The first statement about nephridia is correct.
- The second statement about metameric segmentation is correct.
- The third statement about being monoceious is wrong (it is dioecious).
- The fourth statement about parapodia is correct.

Thus, the answer is that the third statement is incorrect.