Answer the following question given this paragraph: 

A voltaic cell uses a spontaneous redox reaction to generate an electric current. It is also possible to do the opposite. When an external source of direct current is applied to an electrochemical cell, a reaction that is normally nonspontaneous can be made to proceed. Electrolysis is the process in which electrical energy is used to cause a nonspontaneous chemical reaction to occur. Electrolysis is responsible for the appearance of many everyday objects such as gold-plated or silver-plated jewelry and chrome-plated car bumpers.


Q: A voltaic cell uses what type of reaction to generate an electric current

 Choices:

- spontaneous catalyst

- chemical reaction

- instantaneous redox

- spontaneous redox

A:
spontaneous redox
