The total distance of a is 5 * 900 = 4500m.
The total distance of B is 4.5*900=4050 meters.
B will meet A once every 100 meters, so the frequency =4050/ 100=4 1 time.
Choose B.
(1) 20 14 how to divide the college entrance examination subjects in ordinary high schools?
I. Division of college entrance examination subjects in 20 1