A block is pulled at constant speed along a rough level surface by a rope that makes an angle of 30^o with respect to the horizontal. The applied force along the rope is P. the force of kinetic friction between the block and the surface is 10N.

Which one of the following actions will increase the frictional force on the block?

A. increasing the contact surface area

B. decreasing the contact surface area

C. increasing the weight of the block

D.decreasing the weight of the block

E. increasing the angle made by the rope