An Elevator Is Rising at Constant Speed

An elevator is rising at constant speed.Consider the following statements: I.the upward cable force is constant
II.the kinetic energy of the elevator is constant
III.the gravitational potential energy of the Earth-elevator system is constant
IV.the acceleration of the elevator is zero
V.the mechanical energy of the Earth-elevator system is constant

A) all five are true
B) only II and V are true
C) only IV and V are true
D) all but III are true
E) only I, II, and IV are true