Which of the following is an occupational respiratory disorder?

Have you heard about hypoxia? Try to gather information about it,and discuss with your friends.

Smoking leads to which of the following changes in the blood?

$A$: Emphysema is a chronic obstructive pulmonary disease,causing irreversible distension and loss of elasticity of the alveoli.
$R$: Emphysema is preventable if chronic exposure to smoke (cigarette and others) and pollutants is avoided.

$A$ person involved in stone masonry work is likely to suffer from . . . . . . .

Ravi,who lived at sea level,had around $5$ million $RBC$ per cubic millimeter of his blood. Later when he lived at an altitude of $18,000 \ ft$,he showed around $8$ million $RBC$ per cubic millimeter of blood. This is an adaptation because