Which is true according to the law of conservation of energy?
A.in a closed system, the total amount of energy in the universe keeps on changing
B.The supply of energy is limited, so it is essential to conserve it.
C. in a closed system, energy can be created and destroyed,
D.in a closed system, energy cannot be used faster than it is created,
E.in a closed system, the total energy always remains constant,
