In a "wet sump" oil system, where is the oil contained?

In a "wet sump" oil system, the oil is contained within both the engine and the sump. The sump is essentially a reservoir located at the bottom of the engine where the oil collects after it circulates through the engine components. In this type of system, the oil pump draws oil from the sump to lubricate engine parts, and after its use, the oil returns to the sump. This design is common in many engines because it simplifies the oil circulation and management process, making it easier to maintain a consistent oil supply.

The other options don't accurately represent the functionality of a wet sump system. For example, the inclusion of an external tank, as seen in some dry sump systems, is not a characteristic of wet sump systems, which rely on the sump integrated within the engine itself. Thus, the correct understanding of where the oil is contained in a wet sump oil system is indeed the engine and the sump.