Final answer:
The statement that is true about gas particles is that they are very small but have mass, which makes them matter. Gas particles have no definite shape or volume and collide elastically within their container.
Step-by-step explanation:
The correct statement about gas particles is d) they are very small but have a mass making them matter. Gas particles possess certain characteristics that define their state of matter. Gases consist of tiny particles of matter that are in constant motion, with very small mass compared to the large amounts of empty space between each particle. Gas particles do not have a definitive shape or volume and are separated by distances that are much larger than the particles themselves. These particles collide elastically with each other and the walls of any container they may be in, meaning that there's no net loss of energy from these collisions. The kinetic energy of gas particles, which can be related to their average speed, depends on the temperature of the gas.