Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: 
Like density, the pressure of the air decreases with altitude. There is less air pressing down from above the higher up you go. Look at the bottle pictured below ( Figure below ). It was drained by a hiker at the top of a mountain. Then the hiker screwed the cap on the bottle and carried it down to sea level. At the lower altitude, air pressure crushed it. Can you explain why?.


Question: How does air pressure change as altitude increases?
it decreases
Air pressure decreases as altitude increases.