Answer:
c. the air pressure in mountains is lower than at sea level
Explanation:
It is common knowledge that pressure decreases with altitude. The implication of this is that the pressure at the mountain top is much less than the pressure at sea level.
As we get to higher altitudes, the amount of gas molecules present in air decreases rapidly. That is, the air becomes less dense than air nearer to sea level. Hence the expression; "pressure decreases with height".
