The segments in which chaetae are lacking 

Options

A. 1. `1^(st), 2^(nd)`, last
B. 2. `3^(rd),` last, clitellar
C. 3. `1^(st)`, last, clitellar
D. 4. `5^(th), 6^(th)`, last

Answer

To solve the question regarding the segments in which chaetae are lacking in earthworms, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Chaetae**: Chaetae are bristle-like structures found on the segments of earthworms. They are primarily made of a polysaccharide called chitin.

2. **Identifying the Structure of Earthworm**: The earthworm's body is segmented. Each segment may or may not have chaetae.

3. **Segments Without Chaetae**:
- The **first segment** of the earthworm does not have chaetae.
- The **last segment** also lacks chaetae.
- The **clitellum**, which is a thicker, glandular section of the earthworm, also does not have chaetae.

4. **Conclusion**: Therefore, the segments in which chaetae are lacking are the **first segment**, the **last segment**, and the **clitellum**.

5. **Final Answer**: The correct answer is **first, last, and clitellum**.