Answer: The correct answer is increase.
Explanation:
The efficiency of the machine is defined as the output work of a machine compared to the input work.
The output work for a machine cannot be greater than input work. As some of the energy is loss due to friction. The efficiency of a machine can be increased by reducing friction include using the slippery substance like oil.
Besides a reduction in friction the only way to increase the amount of work output of a machine is to increase the work input.
