How is a liquid fundamentally different from a gas?

A. one is wet and one is dry

B. one is hot and one is cold

C. one flows and one does not flow

D. one's atomic particles are moving faster than the other's

Fluids have weak atomic bonds and are stable; if you leave some water in a bowl, the liquid won't move unless you force it to do so. Gas particles constantly move even if you don't exert any external influence on them. So the answer is D.