Option C : Both (A) and (R) are true and (R) is the correct explanation of (A). Explanation : At higher altitudes, the air pressure is lower than at sea level. This means there is less atmospheric pressure to push oxygen into the lungs, which can make it more difficult for the body to get the oxygen it needs. This condition can lead to altitude sickness, which can cause symptoms such as difficulty breathing and heart palpitations, among others. This is the basis for the statement (A) and the reason given in statement (R) accurately explains this situation.