Why do clouds look gray when there is a storm?

However, rain clouds are gray instead of white because of their thickness, or height. That is, a cloud gets thicker and denser as it gathers more water droplets and ice crystals — the thicker it gets, the more light it scatters, resulting in less light penetrating all the way through it.

Ithink d would be correct

The name may be in importnce  to them