Chronic disorder in which alveolar wall are damaged due to which respiratory surface is decreased. One of the major causes of this is cigarette smoking:-

The correct option is B Emphysema
Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. One of the major causes of this is cigarette smoking.
Asthma is a condition in which airways are narrow and swell and may produce extra mucus.
Bronchitis is inflammation of the lining of bronchial tubes, which carry air to and from the lungs.
Fibrosis of lungs is a lung disease that occurs when lung tissue becomes damaged and scarred.

So, the correct answer is 'emphysema.'