What happens to air as altitude decreases

The air gets "thicker".

Explanation:

The amount of oxygen in air increases in the as the altitude decreases or comes down.

sectionalism continues to divide the nation as the question of slavery being allowed in the mexican cession became a problem. -the results of the mexican war spark secession in the south because the north did not want to allow slavery in the territories won.

answer; by working independently, the states have a high likelihood of developing innovative solutions that can be employed in other states;