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.

yes, because even though a theory has a  lot of evidence to support it, it is not always true