Correct option is A
Real-world machines always have energy losses (like friction, heat). So
efficiency can never reach 100%.
This means that the output work is always less than the input work.
The efficiency of a machine is the ratio of the useful work done by the machine to the total energy consumed by the machine.
Friction between the moving parts of a machine causes energy loss in the form of heat.
This loss of energy means that the output of a machine is always less than the input.
