Assertion : Coughing and sneezing are necessary.
Reason : Coughing and sneezing are reflex actions.

Answer

b

Explanation

coughing and sneezing are necessary to take place because these reactions serve to keep the air passages free from foreign matter. Coughing isa reflex action under nercous control. The minute receptors found in the wall of trachea , brochi , bronchioles and alveoli are highly sensitive to foeign matter( smoke , dust etc.) like coughing , sneezing is also a reflex action triggered becouse of irritation to nasal passages, in this , sensory impulses travel from nasal passage to the medulla through trigeminal nerves. the reaction involves the same series of events as in cough reflex , but the air explodes out both through nose and mouth, expelling the foreign matter from nasal passage.