Which reservoir is formed by the Oroville Dam?

The reservoir formed by the Oroville Dam is Lake Oroville. This dam, located on the Feather River in Northern California, was built to provide water storage for agricultural use, flood control, and hydroelectric power generation. The creation of Lake Oroville was a direct result of the construction of the Oroville Dam, which impounds the river, creating the lake.

The other options, while significant bodies of water in California, are associated with different dams. Folsom Lake is created by the Folsom Dam, Shasta Lake is formed by Shasta Dam, and San Luis Reservoir is associated with the San Luis Dam. Each reservoir serves distinct water management purposes within the state's overall water system. Thus, the identification of Lake Oroville as the correct answer is based on its direct connection to the Oroville Dam.