which is the best statement of the law of conversation of energy

The amount of energy put out by a simple machine must equal the amount of energy put into a machine
the amount of energy put into a simple machine should be conserved
the amount of energy put out by a simple machine is always less than the amount of energy put into the machine
the amount of energy put out by a simple machine depends on its efficiency

The amount of energy put into a simple machine should be conserved.