An elevator is rising at constand speed. Consider the subsequent 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) only I,II, III are true
E) only I,II, and IV are true