Which of the following is not a naturally occurring part of Earth's atmosphere? A. gases such as oxygen
B. gases such as carbon dioxide
C. dust and other tiny solid particles
D. sulfur oxides from factories

D

Explanation:

I think it would be D because it says, "from factories" which gives us a clue it's not coming from Earth's atmosphere.

D. sulfur oxides from factories

Explanation:

This does not naturally occur, only if there is a factory. These other things happen on their own in nature but sulfur from factories relies on other factors down on earth.

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs