The correct answer is D. Spasm in bronchial muscles.
Asthma is a chronic respiratory disease that causes inflammation and narrowing of the airways. This makes it difficult to breathe. Asthma can be triggered by a variety of things, including allergies, exercise, cold air, and stress.
The symptoms of asthma include wheezing, coughing, chest tightness, and shortness of breath. These symptoms can be mild to severe, and they can come and go over time.
There is no cure for asthma, but there are treatments that can help to control the symptoms. These treatments include medications, such as inhalers, and lifestyle changes, such as avoiding triggers.
A. Infection of trachea is not the cause of asthma. The trachea is the windpipe, and it is not involved in asthma.
B. Infection of lung is not the cause of asthma. The lungs are the organs that take in oxygen and release carbon dioxide. They are not involved in asthma.
C. Bleeding into pleural cavity is not the cause of asthma. The pleural cavity is the space between the lungs and the chest wall. It is not involved in asthma.
D. Spasm in bronchial muscles is the cause of asthma. The bronchial muscles are the muscles that surround the airways. When they spasm, they narrow the airways, making it difficult to breathe.