What type of energy conversion takes place in an electrolytic cell?

a) chemical energy is spontaneously converted to electrical energy

b) chemical energy is converted to electrical energy only when there is an external power source

c) electrical energy is spontaneously converted to chemical energy

d) electrical energy is converted to chemical energy only when there is an external power source

It would be that Electrical energy is converted to chemical energy only when there is an external power source because there are both kinds of cells that are electrochemical to which an arode is an electrode to which there is half-reaction on the oxidation and another half-reaction on the reduction but only for the electrode cathode. The main cell that converts chemical energy into electrical energy is a called the Galvanic energy. 

Iwould you figure it out but you don't have a picture or in your question as to what the physical property you're looking for is

The answer is not c