A lake created by placing a dam on a river is known as which of the following?

A lake created by placing a dam on a river is referred to as a reservoir. This term specifically denotes an artificial lake used to store water for various purposes, such as irrigation, hydroelectric power generation, water supply, and recreation. Reservoirs are formed when a dam obstructs the flow of a river, causing water to back up and create a larger body of water upstream.

In contrast, backwater typically refers to a section of a river or creek where the flow is impeded, but it’s not usually classified as a full lake or reservoir. A quarry is an excavation site where rocks, minerals, or other materials are extracted, not a body of water. A swimming hole usually describes a natural body of water deep enough for swimming, often found in rivers or lakes but not created artificially by a dam. Thus, "reservoir" is the precise term for a dam-created lake due to its clear association with water management and storage functionality.