A man thinks to remain in equilibrium by pushing in his hands and feet against two vertical parallel walls as the shown in the figure :
a) He must exert equal forces on both walls
b) The forces of friction at both walls must be equal
c) The coefficients of friction between man and wall must be the same at both ends
d) Friction must be present on both walls.

Options

A. a and b are correct
B. a and c are correct
C. a and d are correct
D. all correct

Answer

C