Why is air considered a homogeneous mixture

Explanation:

Because each layer of the Earth's atmosphere has a different density, each layer of air is its own homogeneous mixture.

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.

16

explanation:

the marks go by 4s