The air pressure descends as we ascend. In other words, they are inversely proportional.
The air pressure descends as we ascend the mountain because the air molecules that are above us in high altitudes are fewer than the number of air molecules that are above us in the base of the mountain. So, the exerted pressure of the molecules on ourselves is lower in high altitudes.
Due to the reason mentioned above, we can deduce that the only correct option is option number two since the other ones show increasing or the same pressure, which is not possible as we ascend.
