Why does liquid water take the shape of a cup it is poured into, but solid ice cubes do not?

A
Because the molecules of liquid water are softer than the molecules of solid ice.

B
Because the molecules of liquid water are smaller than the molecules of solid ice.

C
Because the molecules of liquid water are moving but the molecules of solid ice are not.

D
Because the molecules of liquid water can easily move past one another but the molecules of solid ice cannot.