Which of the following statements about hepatitis-B is incorrect?

Options

A. It is one of the examples of STD
B. It is spread primarily by sexual contact, even by contaminated syringes and blood transfusion
C. It is 42 nm enveloped virus containing ss-RNA as the genetic material
D. Recombivax HB, vaccine is available to prevent hepatitis-B infection

Answer

To determine which statement about hepatitis B is incorrect, we will analyze each provided statement one by one.

### Step-by-Step Solution:

1. **Identify the Statements**: The question provides several statements about hepatitis B. We need to evaluate each one to find the incorrect one.

2. **Evaluate the First Statement**:
- "It is one of the examples of STD."
- **Analysis**: Hepatitis B is indeed classified as a sexually transmitted disease (STD).
- **Conclusion**: This statement is **true**.

3. **Evaluate the Second Statement**:
- "It is spread primarily by sexual contact, even by contaminated syringes and blood transfusion."
- **Analysis**: Hepatitis B can be transmitted through sexual contact, as well as through contaminated syringes and blood transfusions.
- **Conclusion**: This statement is **true**.

4. **Evaluate the Third Statement**:
- "It is a 42 nm enveloped virus containing single-stranded RNA as the genetic material."
- **Analysis**: This statement is incorrect because hepatitis B is actually a 42 nm enveloped virus, but it contains double-stranded DNA, not single-stranded RNA.
- **Conclusion**: This statement is **false**.

5. **Evaluate the Fourth Statement**:
- "Recombivax HB vaccine is available to prevent hepatitis B infection."
- **Analysis**: The Recombivax HB vaccine is indeed available and is used to prevent hepatitis B infection.
- **Conclusion**: This statement is **true**.

6. **Final Conclusion**: The incorrect statement about hepatitis B is the third one, which incorrectly describes its genetic material.

### Answer:
The incorrect statement about hepatitis B is: "It is 42 nm enveloped virus containing single-stranded RNA as the genetic material."

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