Question

Why does air have weight?

Answer 1

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. 

Answer 2

Answer:

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

Explanation:

Everything that has mass has weight as well. as with air it is made of molecules with masses which means that air is a form of matter that occupies space and has mass as well.anything that has occupies space and has mass is definitely going to have weight.

Air has weight because air can fill up its entire volume where it is found exerting pressure on the volume, like with the pressure been felt when the wind blows heavily above the sea level. Air has weight because of the mass molecules it contains in it. air is made of oxygen and mostly Nitrogen and these elements have mass and occupies space where ever they are found giving air the weight as well.