Answer: Option (b) is the correct answer.
Step-by-step explanation:
When useful energy is conserved then this conservation is known as energy conservation.
For example, when lights of a room are switched on where no one is sitting then on switching off the lights we are conserving wastage of electricity.
Thus, we can conclude that out of the given options, the statement energy resources can be conserved by turning off lights when they are not in use is true.