A person goes to high altitude and experiences 'altitude sickness' with symptoms like breathing

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
altitudes,
the body does not get sufficient oxygen.
In light of the above statements, choose the correct
answer from the options given below.
1.(A) is true but (R) is false.
2.(A) is false but (R) is true.
3. Both (A) and (R) are true and (R) is the correct
explanation of (A).
4. Both (A) and (R) are true but (R) is not the correct
explanation of (A).