Answer the following question given this paragraph: 

A type of work called expansion work (or pressure-volume work) occurs when a system pushes back the surroundings against a restraining pressure, or when the surroundings compress the system. An example of this occurs during the operation of an internal combustion engine. The reaction of gasoline and oxygen is exothermic. Some of this energy is given off as heat, and some does work pushing the piston in the cylinder. The substances involved in the reaction are the system, and the engine and the rest of the universe are the surroundings. The system loses energy by both heating and doing work on the surroundings, and its internal energy decreases. (The engine is able to keep the car moving because this process is repeated many times per second while the engine is running. ) We will consider how to determine the amount of work involved in a chemical or physical change in the chapter on thermodynamics.


Q: What type of work called occurs when a system pushes back the surroundings against a restraining pressure?

 Choices:

- shape work

- contrast work

- retention work

- expansion work

A:
expansion work
