Which one of the following is a sexually transmitted disease ?

Options

A. Cancer
B. Syphilis
C. Diphtheria
D. Myocarditis

Answer

To determine which one of the following is a sexually transmitted disease (STD), we will analyze each option provided:

1. **Cancer**:
- Cancer is not a contagious disease. It does not spread from one person to another. It is primarily caused by mutations in the DNA, which can be influenced by factors such as tobacco use, alcohol consumption, and environmental factors. Therefore, cancer is not an STD.

2. **Syphilis**:
- Syphilis is caused by the bacterium *Treponema pallidum*. It is transmitted through sexual contact, making it a classic example of a sexually transmitted disease. Therefore, syphilis is indeed an STD.

3. **Diphtheria**:
- Diphtheria is a bacterial infection that affects the respiratory system and is spread through respiratory droplets when an infected person coughs or sneezes. It is not transmitted through sexual contact, so it is not an STD.

4. **Myocarditis**:
- Myocarditis refers to the inflammation of the heart muscle, often caused by viral infections. While it can be associated with viral transmission, it is not classified as a sexually transmitted disease.

Based on this analysis, the correct answer to the question is **syphilis**, as it is the only option that qualifies as a sexually transmitted disease.

### Summary:
- **Correct Answer**: Syphilis (Option 2)