Which of the Assumptions of the Kinetic-Molecular Theory Best Explains

Which of the assumptions of the kinetic-molecular theory best explains the observation that a gas can be compressed?

A) Gas molecules move at random with no attractive forces between them.
B) The velocity of gas molecules is proportional to their Kelvin temperature.
C) The amount of space occupied by a gas is much greater than the space occupied by the actual gas molecules.
D) In collisions with the walls of the container or with other molecules,energy is conserved.
E) Collisions with the walls of the container or with other molecules are elastic.