Simple squamous epithelium would be found in the following areas of the body :

Options

A. A.blood vessels
B. B.respiratory surface of lungs
C. C.lining of body cavities
D. D.(1), (2) and (3) are correct

Answer

### Step-by-Step Solution:

1. **Understanding Simple Squamous Epithelium**:
- Simple squamous epithelium consists of a single layer of flat cells. This type of epithelium is characterized by its thinness, which allows for easy diffusion and filtration.

2. **Identifying Locations**:
- Simple squamous epithelium is typically found in areas where rapid exchange of materials is necessary. This includes:
- **Blood Vessels**: The endothelium (inner lining) of blood vessels is made up of simple squamous epithelium, allowing for efficient transport of nutrients and gases.
- **Respiratory Surface of Lungs**: The alveoli (air sacs) in the lungs are lined with simple squamous epithelium, facilitating gas exchange (oxygen and carbon dioxide).
- **Lining of Body Cavities**: The mesothelium, which lines body cavities (such as the pleura, peritoneum, and pericardium), is also composed of simple squamous epithelium.

3. **Conclusion**:
- Since all the mentioned areas (blood vessels, respiratory surfaces of lungs, and lining of body cavities) are indeed composed of simple squamous epithelium, the correct answer is that all options (1, 2, and 3) are correct.

### Final Answer:
- **Simple squamous epithelium is found in blood vessels, respiratory surfaces of lungs, and lining of body cavities. Therefore, the correct answer is 1, 2, and 3.**

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