will flow toward areas of lower pressure in valleys. will flow toward areas of higher pressure in valleys. is considered to be less dense than warmer air. is considered to be free of oxygen atoms.
I gave my students this multiple choice question: When cold air is at the tops of mountains, the air

Only one answer is correct among these 4 choices:
- will flow toward areas of lower pressure in valleys.
- will flow toward areas of higher pressure in valleys.
- is considered to be less dense than warmer air.
- is considered to be free of oxygen atoms.

Could you tell me which one is correct?

will flow toward areas of lower pressure in valleys.