Which one of the following statements is true?

Options

A. Dysentry, plague and diphtheria are viral diseases.
B. HIV replicates in host cell with the help of reverse transcriptase enzyme.
C. The disease ringworm disappcars during summer and rainy season.
D. Common cold could be confirmed by Widal test.

Answer

To determine which statement is true among the given options, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Analyze Option 1**:
- The statement claims that Dysentery, Plague, and Diphtheria are viral diseases.
- **Fact Check**: Dysentery is caused by Shigella bacteria, Plague is caused by Yersinia pestis bacteria, and Diphtheria is caused by Corynebacterium diphtheriae bacteria.
- **Conclusion**: This statement is **false**.

2. **Analyze Option 2**:
- The statement claims that HIV replicates in host cells with the help of the reverse transcriptase enzyme.
- **Fact Check**: HIV (Human Immunodeficiency Virus) indeed attaches to a host cell, and its RNA is converted into DNA by the enzyme reverse transcriptase. This DNA then integrates into the host's DNA and leads to the production of viral proteins.
- **Conclusion**: This statement is **true**.

3. **Analyze Option 3**:
- The statement claims that the disease ringworm disappears during summer and rainy seasons.
- **Fact Check**: Ringworm is a fungal infection that thrives in warm and humid conditions, which are prevalent during summer and rainy seasons. Therefore, it is unlikely to disappear during these times.
- **Conclusion**: This statement is **false**.

4. **Analyze Option 4**:
- The statement claims that common cold could be confirmed by the Vidal test.
- **Fact Check**: The Vidal test is used to diagnose enteric fever and typhoid, not the common cold. The common cold is usually diagnosed based on symptoms.
- **Conclusion**: This statement is **false**.

### Final Conclusion:
After analyzing all four statements, the only true statement is **Option 2**: "HIV replicates in host cell with the help of reverse transcriptase enzyme."

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