$\underline {\text { Variable } }$ Atmospheric Components Refer to
A) Only Natural Gases and Materials

$\underline {\text { Variable } }$ atmospheric components refer to

A) only natural gases and materials.
B) nitrogen, oxygen, argon, and carbon dioxide.
C) natural sources of dust and aerosols, such as volcanic dust and forest fire smoke, but nothing anthropogenic (human-caused) .
D) both natural and anthropogenic gases and materials.