Every real machine:

A. must be more than 100% efficient

B. must be equal to 100% efficient

C. must be less than 100% efficient

No machine can operate at 100 percent efficiency because some of the energy input will always be used to overcome the force of gravity and the effects of friction and air resistance. Even an optimally tuned engine heats up eventually, and that heat is thermal energy being lost. So C. will be your Best answer.