Asthma is a respiratory disease caused by:

Options

A. Infection of trachea
B. Infection of lungs
C. Bleeding into pleural cavity
D. Spasm in bronchial muscles.

Answer

**Step-by-Step Solution:**

1. **Definition of Asthma**: Asthma is a respiratory condition characterized by the narrowing and swelling of the airways, along with the production of excess mucus.

2. **Mechanism of Asthma**: The condition is primarily an allergic reaction involving mast cells in the lungs. When allergens enter the respiratory system, the immune system responds, leading to inflammation.

3. **Symptoms**: Common symptoms of asthma include coughing, wheezing, and a feeling of tightness in the chest.

4. **Underlying Cause**: Asthma is often referred to as bronchial asthma, which indicates that the spasms occur in the bronchioles, leading to a reactive airway disease.

5. **Role of Allergens**: Allergens trigger the immune response, causing the release of chemicals that lead to inflammation and other allergy symptoms such as sneezing and coughing.

6. **Conclusion**: Therefore, asthma is a respiratory disease caused by spasms in the bronchial muscles, leading to restricted airflow and difficulty in breathing.

**Final Answer**: Asthma is a respiratory disease caused by spasm in bronchial muscles.

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