How many of following belong to antibiotic ?
Crocin , penicillin , streptomycin , `KMnO_4,SO_2`

Answer

To determine how many of the given substances belong to the category of antibiotics, we will analyze each substance one by one.

### Step-by-Step Solution:

1. **Identify the substances**: The substances we need to analyze are Crocin, Penicillin, Streptomycin, KMnO4, and SO2.

2. **Define antibiotics**: Antibiotics are antimicrobial drugs used to treat and prevent bacterial infections by inhibiting the growth of bacteria.

3. **Analyze Crocin**:
- Crocin is primarily known as a painkiller and is used to relieve pain and reduce fever.
- **Conclusion**: Crocin is **not an antibiotic**.

4. **Analyze Penicillin**:
- Penicillin is a well-known antibiotic that is effective against a variety of bacterial infections.
- **Conclusion**: Penicillin is **an antibiotic**.

5. **Analyze Streptomycin**:
- Streptomycin is another antibiotic that is used to treat infections caused by certain bacteria.
- **Conclusion**: Streptomycin is **an antibiotic**.

6. **Analyze KMnO4 (Potassium Permanganate)**:
- KMnO4 is commonly used as a disinfectant and antiseptic but is not classified as an antibiotic.
- **Conclusion**: KMnO4 is **not an antibiotic**.

7. **Analyze SO2 (Sulfur Dioxide)**:
- SO2 is a chemical compound that is primarily used as a preservative and in various industrial applications. It does not have antibiotic properties.
- **Conclusion**: SO2 is **not an antibiotic**.

8. **Count the antibiotics**:
- From our analysis, the antibiotics identified are Penicillin and Streptomycin.
- Therefore, the total number of antibiotics in the list is **2**.

### Final Answer:
**2** substances from the list belong to the category of antibiotics.

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