Which property of gases is explained by the process of diffusion? A.
their ability to compress under high temperature
B.
their ability to expand under low temperature
C.
their ability to expand under pressure
D
their ability to fill the available volume of a container

The appropriate alternative is "Option D".

Explanation:

Diffusion would be a random or physical phenomenon that corresponds to that same transfer budget of molecules from some kind of highly concentrated area to something like a lower one. The substance which diffuses may be strong, liquids, and gaseous. Correspondingly, the framework where certain diffusion happens can however be amongst the three aspects of sustainability.

All those other options aren't relevant to the situation in question. So the above alternative becomes the right one.