The molecules of a gas are free to move about in any direction. Because of large intermolecular spaces, the gases are easily compressible. The kinetic energy of the molecules of gases is maximum and they move about randomly at a high speed. The randomly moving high speed molecules hit against the sides of containing vessel. The pressure exerted by any gas is due to the force exerted by its molecules on the sides of containing vessel.
A gas fills all the space in a container in which it is kept because

Answer

A

Explanation

The molecules of a gas have large intermolecular spaces and kinetic energy, hence the molecules of gas spread into the entire space of the container.