Which of the following is not a sexually transmitted disease?

Options

A. Trichomoniasis
B. Encephalitis
C. Syphilis
D. Acquired Immuo Deficiency Syndrome

Answer

To determine which of the following is not a sexually transmitted disease (STD), we will analyze each option provided in the question: Trichomoniasis, Encephalitis, Syphilis, and Acquired Immunodeficiency Syndrome (AIDS).

### Step-by-Step Solution:

1. **Identify the Diseases**: The options given are:
- Trichomoniasis
- Encephalitis
- Syphilis
- Acquired Immunodeficiency Syndrome (AIDS)

2. **Define Sexually Transmitted Diseases (STDs)**: STDs are infections that are primarily spread through sexual contact. Common examples include syphilis, gonorrhea, chlamydia, and HIV/AIDS.

3. **Analyze Each Option**:
- **Trichomoniasis**: This is a sexually transmitted disease caused by a parasite. It is commonly spread through sexual intercourse.
- **Encephalitis**: This refers to inflammation of the brain, which can be caused by various infections (viral or bacterial). It is not primarily transmitted through sexual contact.
- **Syphilis**: This is a well-known sexually transmitted disease caused by the bacterium Treponema pallidum. It is spread through sexual contact.
- **Acquired Immunodeficiency Syndrome (AIDS)**: This is caused by the Human Immunodeficiency Virus (HIV) and is transmitted through sexual contact, making it an STD.

4. **Conclusion**: Among the options, Encephalitis is not primarily a sexually transmitted disease. While it can potentially be transmitted through sexual contact in some rare cases, it is not classified as an STD.

### Final Answer:
The disease that is not a sexually transmitted disease is **Encephalitis**.

---