Natural sources of variable atmospheric components includes all of the following sources except
a. automobiles.
b. volcanoes.
c. plants.
d. sea spray.

The top of the atmosphere forms a clean edge with the vacuum of space.
True

False

Parts of the atmosphere are identified primarily by their
a. composition, temperature, function.
b. temperature, color, altitude.
c. altitude, temperature, composition.
d. temperature, density, altitude.