Which of the following is an embryonic connective tissue

Options

A. Endometrium
B. Mediastinum
C. Mesenchyme
D. Endothelium

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks to identify which of the given options is an embryonic connective tissue. The options provided are endometrium, mesometrium, mediastinum, mesenchyme, and endothelium.

2. **Defining Connective Tissue**: Connective tissues are types of tissues that support, bind together, and protect tissues and organs of the body. They consist of cells and an extracellular matrix, which includes ground substance and fibers.

3. **Identifying Embryonic Connective Tissue**: Among the options, we need to identify which one is classified as embryonic connective tissue.

4. **Analyzing the Options**:
- **Endometrium**: This is the inner lining of the uterus and is not a connective tissue.
- **Mesometrium**: This refers to the part of the broad ligament of the uterus and is not classified as connective tissue.
- **Mediastinum**: This is an anatomical region in the thoracic cavity and does not refer to connective tissue.
- **Mesenchyme**: This is a type of embryonic connective tissue that is found in the developing embryo. It consists of loosely organized cells that can differentiate into various cell types.
- **Endothelium**: This is a thin layer of cells lining the blood vessels and is not a connective tissue.

5. **Conclusion**: The only option that fits the description of embryonic connective tissue is **mesenchyme**. Therefore, the correct answer is **mesenchyme**.

### Final Answer:
The correct answer is **mesenchyme**.