Assertion : At higher peaks of mountains, people suffer from high altitude sickness (sluggish feeling, breathlessness etc.) due to lesser oxygen intake at each breather
Reason : Air at sea level is dense because it is compressed by the mass of the air above it. The atmospheric pressure at higher peaks of mountains is lower causing the air at those heights to be much less dense than at sea level.

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true

Answer

A