Law of conservation of energy states that energy can neither be created nor be destroyed. But it can be transformed from one form to another.
Law of conservation of Mechanical energy states that mechanical energy of the closed system remain constant until dissipative forces are absent. This means that potential energy gets converted in kinetic energy or vice versa.
Mechanical energy is defined as the sum of the both potential and kinetic energies.
M.E = P.E + K.E
So, from the given options the correct answer is option A.
