Which of the following statements is true about gas particles?
they repel each other with a strong force.
there is a lot of empty space between them.
they collide to increase their net kinetic energy.
there is a strong force of attraction between them.

There is a lot of empty space between the gas particles.

There are three states of matter called solid, liquid, and gas. Among them gas have high expanding capability. The gaseous particles have large space between them and they lack definite shape or volume. They doesn't repel with other gaseous particle due to strong force.  

As there is huge space between the particles present in the gas, they occupy the whole space of the substance in which they are kept. The strong attracting force between the particles is seen in case of solids due to which they have definite shape and volume.