Three balls A, B, and C are of masses m, 2m, and 3m respectively, and are placed on a smooth horizontal surface in a line. What is the resulting motion of the system?

a) A, B, and C move to the right
b) A and C move to the left, B remains stationary
c) B moves to the right, A and C remain stationary
d) A, B, and C remain stationary