The main assumptions of the kinetic molecular theory of gases are: 1. gases are made up of molecules which are relatively far apart. 2. the molecules are in motion at high speeds. 3. the molecules are perfectly elastic. 4. increase in temperature increases the kinetic energy of the molecules. the assumption that explains charles' law is:

First of all, Charles' Gas Law indicates that the volume that an amount of gas occupies will increase if you increase the temperature of the gas molecules. Note that when you increase the temperature of the gas molecules, it means that the molecules are moving faster and thus, the kinetic energy stored in the molecules also increase. This is what the Kinetic Molecular Theory of Gases also says. Moreover, since the molecules are moving faster, there is a higher probability of collision with other molecules. So, in order to keep the pressure inside the vessel the same throughout the process, the volume or the space occupied by the gas molecules must also be increased. Thereby, the assumption that explains Charles' Law is 4. Increase in temperature increases the kinetic energy of the molecules. 

astronomers such as edwin hubble.