Which statement describes one characteristic of an operating electrolytic cell?

(1) It produces electrical energy.

(2) It requires an external energy source.

(3) It uses radioactive nuclides.

(4) It undergoes a spontaneous redox reaction.

The answer is (2). The electrolytic cell mechanism is to convert the electrical energy to chemical energy. So it need external energy source. And there is a similar one called voltaic cell which will convert the chemical energy to electrical energy.