(A) create energy.
(B) destroy energy.
(C) convert energy.
(D) extract energy from the aether.
(A) create energy. --- No.
Energy cannot be created.
(B) destroy energy. --- No.
Energy cannot be destroyed.
(C) convert energy. --- Yes.
They convert heat energy
from burning fuel, electrical energy, etc.
to mechanical energy.
(D) extract energy from the aether. --- No.
They convert familiar forms of energy.