A substance produced by the host in response to an infection of foreign structure is

Options

A. Antigen
B. Phytotoxin
C. Antibody
D. Hormone

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a substance produced by the host in response to an infection of a foreign structure. We need to identify what this substance is.

2. **Analyzing the Options**:
- **Antigen**: This is a foreign substance that induces an immune response in the host. It is not produced by the host.
- **Phytotoxin**: This is a toxic substance produced by plants, not related to the human immune response.
- **Antibody**: This is a protein produced by the immune system in response to the presence of antigens (foreign substances).
- **Hormone**: These are signaling molecules produced by glands in the body, not specifically in response to infections.

3. **Identifying the Correct Answer**: The substance that is produced by the host in response to an infection (foreign structure) is **Antibody**. Antibodies are specifically generated to target and neutralize antigens.

4. **Conclusion**: Based on the analysis, the correct answer to the question is **Antibody**.

**Final Answer**: The substance produced by the host in response to an infection of a foreign structure is **Antibody**.

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