Question

An engine is any machine that can _____.

convert an energy input to mechanical energy output

convert an energy input to chemical energy output

convert an energy input to heat energy output

convert an energy input to nuclear energy output

Answer 1

convert an energy input to mechanical energy output

Answer 2

The answer is
A, or convert an energy input to mechanical energy output.

This is because engines transfer whatever energy they need at first into mechanical energy to move. Like car engines. They make mechanical energy to help the car move.