The chitinous bristles that earthworms use to anchor themselves in the earth and pull themselves along are :

Options

A. aortic arches
B. setae
C. parapodia
D. nephridia

Explanation

To solve the question regarding the chitinous bristles that earthworms use to anchor themselves in the earth and pull themselves along, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Earthworms**: Earthworms have a segmented body consisting of 100 to 150 segments. Each segment contains muscles and bristles that aid in movement.

2. **Identify the Function of Bristles**: The bristles in earthworms are used for anchoring themselves in the soil and assisting in locomotion. They help the earthworm grip the soil as it moves.

3. **Know the Term for Bristles**: The specific name for these bristles in earthworms is "setae". Setae are tiny, hair-like structures that are chitinous in nature.

4. **Eliminate Incorrect Options**:
- **Option 1: Auricular arches** - These are embryological structures and not related to the bristles of earthworms.
- **Option 3: Parapodia** - These are paired structures found in polychaete worms, not in earthworms.
- **Option 4: Nephridia** - These are excretory organs in invertebrates and do not refer to the anchoring bristles.

5. **Conclude the Correct Answer**: Based on the above analysis, the correct answer is "setae", which corresponds to option number two.

### Final Answer:
The chitinous bristles that earthworms use to anchor themselves in the earth and pull themselves along are called **setae**.

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