Membrane separating air in pulmonary alveoli from blood capillaries is :

Options

A. Alveolar epithelium
B. Cardiac epithelium
C. Capillary endothelium
D. Both (a) &(b)

Answer

To answer the question regarding the membrane that separates air in the pulmonary alveoli from blood capillaries, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for the specific membrane that separates the air in the pulmonary alveoli from the blood in the capillaries.

2. **Identify the Options**: The options provided are:
- A) Alveolar epithelium
- B) Cardiac epithelium
- C) Capillary endothelium
- D) Both A and B

3. **Evaluate Each Option**:
- **Option A: Alveolar Epithelium**: This is the lining of the alveoli and is indeed responsible for the gas exchange process. It is also known as the respiratory membrane, which separates the air in the alveoli from the blood in the capillaries.
- **Option B: Cardiac Epithelium**: This refers to the lining associated with the heart and is not relevant to the alveoli or gas exchange. Thus, this option is incorrect.
- **Option C: Capillary Endothelium**: This is the inner lining of blood vessels, including capillaries, but it does not specifically refer to the membrane separating alveoli from blood. Therefore, this option is also incorrect.
- **Option D: Both A and B**: Since option B is incorrect, this option cannot be correct either.

4. **Conclusion**: Based on the evaluation, the correct answer is **Option A: Alveolar epithelium**. This membrane allows for the exchange of gases (oxygen and carbon dioxide) between the alveoli and the blood capillaries.

### Final Answer:
The membrane separating air in pulmonary alveoli from blood capillaries is **Alveolar epithelium**.