Question

question 2
atmosphere:
most of the mass in the atmosphere is located here.
in the first~18 km above the surface
from 18-160 km above the surface
from 50- 80 km above the surface
from 18-50 km above the surface

Explanation:

The troposphere, which extends up to about 18 km above the Earth's surface for the equator (and varies at different latitudes), contains most of the atmosphere's mass due to the pull of gravity and the presence of most of the water - vapor and weather - related phenomena.

Answer:

In the first~18 km above the surface