Which of the following is not a sexually transmitted disease ?

Options

A. Acquired Immuno Deficiency Syndrome (AIDS)
B. Trichomoniasis
C. Encephalitis
D. Syphilis

Answer

To determine which of the following is not a sexually transmitted disease (STD), we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding STDs**:
- Sexually transmitted diseases (STDs) are infections that are primarily spread through sexual activity, which includes anal, vaginal, and oral sex.

2. **Analyzing the Options**:
- **Option A: Acquired Immunodeficiency Syndrome (AIDS)**:
- AIDS is caused by the Human Immunodeficiency Virus (HIV) and is transmitted through sexual contact, making it an STD.
- **Option B: Trichomoniasis**:
- Trichomoniasis is an infection caused by the parasite Trichomonas vaginalis and is also transmitted through sexual activity, classifying it as an STD.
- **Option C: Encephalitis**:
- Encephalitis is an inflammation of the brain, usually caused by viral infections. It is not transmitted through sexual contact, therefore it is not an STD.
- **Option D: Syphilis**:
- Syphilis is a bacterial infection that is transmitted through sexual contact, making it an STD.

3. **Conclusion**:
- Based on the analysis, the option that is not a sexually transmitted disease is **Option C: Encephalitis**.

### Final Answer:
**C. Encephalitis**

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