Which of the following statement is incorrect about annelida?

Options

A. They are triploblastic, metamerically segmented coelomate animals
B. they possess both longitudinal and circular muscles which help in locomotion
C. A closed circularotry system is present
D. All are monoecious and reproduction is sexual

Explanation

### Step-by-Step Solution:

1. **Understanding Annelida**: Annelids are segmented worms that belong to the phylum Annelida. They are characterized by their segmented bodies and organ system level of organization.

2. **Analyzing the Options**:
- **Option A**: "They are triploblastic metamerically segmented coelomate animals."
- This statement is correct. Annelids are indeed triploblastic (having three germ layers) and coelomate (having a true body cavity), and they exhibit metameric segmentation.

- **Option B**: "They possess both longitudinal and circular muscles which help in locomotion."
- This statement is also correct. Annelids have both types of muscles that facilitate movement.

- **Option C**: "A closed circulatory system is present."
- This statement is correct as well. Annelids possess a closed circulatory system where blood is contained within vessels.

- **Option D**: "All are monoecious and reproduction is sexual."
- This statement is incorrect. While some annelids are monoecious (having both male and female reproductive organs), many are dioecious (having separate sexes), and they can reproduce both sexually and asexually.

3. **Identifying the Incorrect Statement**: Based on the analysis, the incorrect statement is Option D: "All are monoecious and reproduction is sexual."

4. **Conclusion**: The answer to the question is Option D.