Leech does not allow blood clotting by

Options

A. Heparin
B. Thromboplastin
C. Hirudin
D. Haemophiliac factor

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about how leeches prevent blood clotting in their hosts while feeding.

2. **Identifying the Options**: The options provided are:
- Heparin
- Thromboplastin
- Hirudin
- Hemophilic factor

3. **Analyzing Each Option**:
- **Heparin**: This is an anticoagulant found in the human body, particularly in the liver. However, it is not produced by leeches.
- **Thromboplastin**: This substance is involved in the blood clotting process, promoting clot formation, so it does not prevent clotting.
- **Hirudin**: This is a peptide that acts as a potent anticoagulant and is naturally secreted by leeches to prevent blood clotting in their hosts.
- **Hemophilic factor**: This refers to factors that are necessary for blood clotting, so it does not prevent clotting.

4. **Conclusion**: The correct answer is **Hirudin**, as it is the substance that leeches secrete to prevent blood clotting in their hosts.

5. **Final Answer**: Leeches do not allow blood clotting by **Hirudin**.

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