B distance is related to two factors: time and speed. Although the speed of car A is faster than that of car B, it is only on the premise of the same time, so this option is wrong;
C, although the average speed of car A is greater than that of car B, their mass is not considered, so it is impossible to compare their kinetic energy, so this option is wrong;
D. According to the calculation result of A, the average speed of car A is greater than that of car B, so the distance between car A and car B increases with time, so this option is correct.
So choose D.