Use reasoning to lead to the answer of the following question:
George checked the rotor of the Apache, which wasn't powered by internal combustion, but by what?\nOptions:\n- jet engine\n- helicopter\n- electric motor\n- rotator\n- electrical circuit

jet engine
A rotor can be powered by a jet engine.

Jet engine has electric motor fitted in whih helps to power up the rotor.

.

The final answer: jet engine