Read the following excerpt from a student essay. How can the writer best improve his or her ideas and development?
Asthma is a lung condition that makes it difficult to breathe. When people have asthma, their breathing passages can become inflamed, swelling up and filling with mucus. Emphysema is another lung disease that makes people short of breath. In people with asthma, inflamed airways become sensitive to smoke and dust, and as a result, the muscles of the airway can tighten up. All of these things make the passages narrow, so it's hard for air to move through. As a result, people with asthma sometimes have a hard time breathing.
A. by including more details to support the main idea
B. by clearly stating the main idea
C. by removing information unrelated to the main idea
Identify the correct option from the choices provided and respond with the letter of the correct option.

C