Asthma' is due to

Options

A. (1) infection of lungs
B. (2) bleeding into pleural cavity
C. (3) infection of trachea
D. (4) spasm of bronchial muscles

Answer

**Step-by-Step Solution:**

1. **Understanding Asthma**: Asthma is a chronic respiratory condition that affects the airways in the lungs. It is characterized by episodes of wheezing, coughing, chest tightness, and shortness of breath.

2. **Identifying Causes**: The question asks what asthma is due to. The options provided are:
- A) Infection of lungs
- B) Bleeding into pleural cavity
- C) Infection of trachea
- D) Spasm of bronchial muscles

3. **Analyzing Each Option**:
- **Option A (Infection of lungs)**: While lung infections can cause respiratory issues, they are not the primary cause of asthma.
- **Option B (Bleeding into pleural cavity)**: This condition is unrelated to asthma and involves different respiratory complications.
- **Option C (Infection of trachea)**: Similar to lung infections, tracheal infections can cause respiratory symptoms but are not the cause of asthma.
- **Option D (Spasm of bronchial muscles)**: This is the correct option. Asthma is primarily caused by spasms in the bronchial muscles, which leads to narrowing of the airways, making it difficult to breathe.

4. **Conclusion**: The correct answer is D) Spasm of bronchial muscles. This condition is often triggered by environmental factors (like allergens) and can also have genetic components.

5. **Symptoms of Asthma**: The common symptoms include coughing, chest tightness, and shortness of breath, which are directly related to the spasms in the bronchial muscles.