Why does air have weight?

A) Because everything has weight

B) The force of gravity acts on the air molecules' mass

C) The pressure of the air molecules colliding with D) each other gives them weight

E) Air fills its entire volume, producing weight

Air is made of molecules of matter, which have mass, and thus air also has mass. So, the correct answer as to why air has weight is B. the force of gravity acts on the air molecules' mass, and so weight is created.

You can actually feel the air's weight when the wind is blowing, for example.