Breathing And Exchange Of Gases

Given below are two statements : one is labelled as
Assertion (A) and the other is labelled as Reason
(R).

Assertion (A) : A person goes to high altitude and experiences "Altitude Sickness" with symptoms like breathing difficulty and heart palpitations.

Reason (R) : Due to low atmospheric pressure at high altitude, the body does not get sufficient oxygen.

In the light of the above statements, choose the
correct answer from the options given below :