Which of the following could be a possible reason for difficulty in cooking on the mountain?

Atmospheric pressure increases with altitude

Atmospheric pressure is that pressure which is exerted by a mercury column of 76 cm length at 0oC at 45o latitude at the sea-level.

Atmospheric pressure decreases with altitude (height from earth's surface). This is why:

1. It is difficult to cook on the mountain.

2. The fountain pen of a passenger leaks in airplane at height.