Question

which pair of molecules both contain carbon atoms?
o fats and proteins
o water and carbohydrates
o nucleic acids and water
o oxygen gas and fats

Explanation:

Carbon is a key element in organic compounds. Fats and proteins are organic molecules, with fats being triglycerides and proteins being polymers of amino - acids, both containing carbon. Oxygen gas ($O_2$) is an inorganic molecule and does not contain carbon. Water ($H_2O$) is also inorganic and lacks carbon. Nucleic acids contain carbon, but water in the nucleic - acids and water pair doesn't change the fact that water itself is carbon - free. Water and carbohydrates pair: water has no carbon.

Answer:

fats and proteins