Anus is absent in

Options

A. Antedon
B. Ophiothrix
C. Holothuria
D. Echinus

Answer

To solve the question "Anus is absent in," we need to analyze the options provided and determine which organism does not possess an anus.

### Step-by-Step Solution:

1. **Understanding the Options**:
- The options provided are:
- A) Antidone
- B) Ophiothrix
- C) Holothuria
- D) Echinus

2. **Identifying the Phylum**:
- All the options belong to the phylum Echinodermata, which includes various marine organisms.

3. **Analyzing Each Option**:
- **Antidone**: This organism is known to lack an anus. Instead, it has a unique excretory system where waste is expelled through other means, such as through the body surface or specialized structures.
- **Ophiothrix**: Commonly known as brittle stars, they do possess an anus.
- **Holothuria**: Known as sea cucumbers, they also have an anus.
- **Echinus**: This is the European edible sea urchin, which has an anus.

4. **Conclusion**:
- Based on the analysis, the only organism from the options that is known to lack an anus is **Antidone**.

5. **Final Answer**:
- The correct answer is **A) Antidone**.