Concept:The mean free path is a kinetic theory term that describes the average distance a moving molecule covers between successive collisions.
Explanation:Gas molecules are in constant random motion and repeatedly collide with one another.
After every collision, a molecule travels a certain distance before it hits another molecule.
This distance is not fixed — it changes with each collision.
To describe the motion of the gas, we take the average of all these individual distances over many collisions.
This average distance is called the mean free path.
It depends on the size of the molecules, as well as the pressure and temperature of the gas.
At lower pressure or higher temperature, molecules travel farther between collisions, so the mean free path becomes longer.
Answer:D. Mean free path