A man is standing on a plank which is placed on smooth horizontal surface. There is sufficient friction between the feet of man and plank. Now man starts running over plank, correct statement is /are
A. Work done by friction on man with respect to ground is negative
B. Work done by friction on man with respect to ground is positive
C. Work done by friction on plank with respect to ground is positive
D. Work done by friction on man with respect to plank is zero.
