If an earthworm is left in `40%` KOH solution for a long time, Which part would be left undissolved

Options

A. Setae
B. Spermatheca
C. Sand particles
D. Circular muslces

Answer

To determine which part of an earthworm would be left undissolved when placed in a 40% KOH solution for a long time, we can analyze the composition of the various parts of the earthworm.

### Step-by-Step Solution:

1. **Understand the Composition of Earthworm Parts**:
- Earthworms have various structures including setae, permithica, sand particles, and circular muscles.
- Setae are bristle-like structures made of chitin, which is a nitrogenous organic polymer.
- Permithica and circular muscles are primarily composed of proteins.

2. **Analyze the Effect of KOH**:
- KOH (potassium hydroxide) is a strong alkaline solution. It can dissolve many organic substances, especially proteins.
- Proteins are zwitterions and are susceptible to hydrolysis in alkaline conditions, meaning they can be broken down and dissolved.

3. **Identify the Undissolved Part**:
- Since setae are made of chitin, which is not easily dissolved in alkaline solutions, they would remain intact even after prolonged exposure to KOH.
- In contrast, the permithica, sand particles, and circular muscles, being primarily protein-based, would likely dissolve in the KOH solution.

4. **Conclusion**:
- The part of the earthworm that would be left undissolved in a 40% KOH solution is the **setae**.

### Final Answer:
The part that would be left undissolved is the **setae**.

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