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

Options

A. blood vessels
B. respiratory surface of lungs
C. liming of body cavities
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 structure allows for efficient diffusion and filtration due to its thinness.

2. **Identifying Locations**:
- Simple squamous epithelium is found in areas of the body where rapid diffusion or filtration is necessary. Key locations include:
- **Blood Vessels**: The endothelium lining the blood vessels is made of simple squamous epithelium, facilitating the exchange of gases and nutrients.
- **Lungs**: Specifically, the alveoli (air sacs) in the lungs are lined with simple squamous epithelium, allowing for the efficient exchange of oxygen and carbon dioxide.
- **Body Cavities**: The lining of body cavities, known as mesothelium, is also composed of simple squamous epithelium, providing a smooth surface that reduces friction between organs.

3. **Evaluating Options**:
- Given the areas mentioned in the question, we can evaluate the options:
- **Option 1**: Blood vessels - Correct, as simple squamous epithelium lines them.
- **Option 2**: Respiratory surface of lungs - Correct, as it is present in the alveoli.
- **Option 3**: Lining of body cavities - Correct, as it forms the mesothelium.
- **Option 4**: All of the above are correct.

4. **Conclusion**:
- Therefore, simple squamous epithelium is found in blood vessels, the respiratory surfaces of the lungs, and the lining of body cavities. The correct answer is that options 1, 2, and 3 are correct.

### Final Answer:
Simple squamous epithelium is found in:
1. Blood vessels
2. Respiratory surfaces of the lungs
3. Lining of body cavities