Due to increasing air-borne allergens and pollutants, many people in urban areas are suffering from respiratory disorder that cause wheezing due to

• A

  reduction in the secretion of surfactant by pneumocytes

• B

  benign growth on mucous lining of nasal cavity

• C

  inflammation of bronchi and bronchioles

• D

  proliferation of fibrous tissues and damage of the alveolar walls.