As can be seen from the figure, after 5s, the distance of A is sa=5m, the distance of B is sb=2.5m, and the distance of C is sc= 1m, indicating that the speed of A is greater than that of B and C,

From the meaning of the question, the speed of a is less than that of b, so b may be a and b, and a may be b and c; - ①

From the meaning of the question, after five seconds of exercise, the distance between A and B is more than 2 meters, while the distance between A and B is more than 2 meters, and the distance between A and C is more than 2 meters. It can be seen that A and B may be B, A, or C, A-②.

According to ① and ②, A may be B, C,

So choose D.