Silk is a secretion by silk worm from its special

Options

A. fat bodies
B. malpigian tubules
C. poison
D. salivary glands

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the source of silk secretion in silkworms. We need to identify the specific organ responsible for this secretion.

2. **Analyzing the Options**: The options provided are:
- a. Fat bodies
- b. Malpighian tubules
- c. Poison
- d. Salivary glands

3. **Identifying the Correct Option**:
- **Fat bodies**: These are involved in energy storage and do not produce silk.
- **Malpighian tubules**: These are excretory organs in insects and are not related to silk production.
- **Poison**: This option does not relate to silk production.
- **Salivary glands**: These are known to secrete substances that contribute to silk production.

4. **Conclusion**: The correct answer is **d. Salivary glands**. The salivary glands of the silkworm produce the proteins that form silk, specifically fibroin and sericin, which are crucial for making the cocoon.

5. **Explanation of Silk Production**:
- Silk is primarily made of fibroin, which is produced in the salivary glands.
- The salivary glands also produce sericin, which acts as a gum-like substance that forms the outer layer of the cocoon.
- During the silk extraction process, the cocoon is usually placed in hot water to help dissolve sericin, allowing the silk threads to be unwound.