The common cold is caused by

Options

A. Rhino viruses
B. Streptococcus pneumoniae
C. Salmonella typhimurium
D. Plasmodium vivax.

Explanation

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks what causes the common cold.

2. **Review the Options**: The options provided are:
- Option 1: Rhinovirus
- Option 2: Streptococcus pneumoniae
- Option 3: Salmonella typhimurium
- Option 4: Plasmodium vivax

3. **Analyze Each Option**:
- **Option 1: Rhinovirus**: This is a virus known to be the primary cause of the common cold. It has approximately 100 different strains.
- **Option 2: Streptococcus pneumoniae**: This is a bacterium that causes pneumonia, not the common cold.
- **Option 3: Salmonella typhimurium**: This bacterium is responsible for causing typhoid fever, not the common cold.
- **Option 4: Plasmodium vivax**: This is a protozoan parasite that causes malaria, not related to the common cold.

4. **Conclusion**: After analyzing all the options, it is clear that the common cold is caused by the rhinovirus.

5. **Final Answer**: The correct answer is **Option 1: Rhinovirus**.

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