The chaetae in setigerous sac are made up of 

Options

A. keratin
B. poryphyrin
C. chitin
D. globin

Answer

To answer the question "The chaetae in setigerous sac are made up of:", we will analyze the options provided and identify the correct one step by step.

### Step-by-Step Solution:

1. **Understanding Chaetae**:
- Chaetae are bristle-like structures found in certain annelids, including earthworms. They are also known as setae.
- These structures are important for locomotion and anchoring in the soil.

2. **Identifying the Composition**:
- The question asks what chaetae are made up of. The options given are keratin, porphyrin, chitin, and globin.

3. **Analyzing Each Option**:
- **Keratin**: This is a fibrous protein found in hair, nails, and the outer layer of skin. It is not found in chaetae.
- **Porphyrin**: This is a compound that forms part of hemoglobin, which is involved in oxygen transport in blood. It is not related to chaetae.
- **Chitin**: This is a polysaccharide that forms the exoskeleton of arthropods and is also found in the chaetae of annelids. It provides structural support.
- **Globin**: This refers to a group of proteins that are part of hemoglobin. Like porphyrin, it is not related to chaetae.

4. **Conclusion**:
- Based on the analysis, the correct answer is **chitin**, as it is the material that makes up the chaetae in the setigerous sac of earthworms.

### Final Answer:
The chaetae in setigerous sac are made up of **chitin**.