Antibiotics are

Options

A. products of metabolism in bacteria
B. collective name of useful bacteria
C. toxins produced by bacteria
D. drugs manufactured to kill viruses

Answer

**Step-by-Step Solution:**

1. **Understanding Antibiotics**: Antibiotics are substances that are used to kill or inhibit the growth of bacteria. They are primarily used to treat bacterial infections.

2. **Identifying Sources**: Antibiotics are often produced by microorganisms, particularly bacteria and fungi. This means that they are natural products of these organisms.

3. **Analyzing the Options**:
- **Option A**: Products of metabolism in bacteria - This is correct as antibiotics are indeed metabolic products of certain bacteria and fungi.
- **Option B**: Collective name for useful bacteria - This is incorrect. While some bacteria are beneficial, antibiotics are not a collective name for them.
- **Option C**: Toxin produced by bacteria - This is misleading. While some bacteria produce toxins, antibiotics are not classified as toxins.
- **Option D**: Drugs manufactured to kill viruses - This is incorrect as antibiotics are specifically designed to target bacteria, not viruses.

4. **Conclusion**: Based on the analysis of the options, the correct answer is **Option A**: Products of metabolism in bacteria.

**Final Answer**: Antibiotics are products of metabolism in bacteria (Option A).

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