RESTRICTED DATA is defined in which act?

The correct answer is rooted in the specific definitions provided in U.S. legislation regarding sensitive information related to atomic energy. The term "RESTRICTED DATA" is defined in the Atomic Energy Act of 1954. This act was established to regulate the development, use, and control of atomic energy and materials, and it categorizes information deemed critical to national security concerning nuclear weapons and energy.

Under this act, any data that could compromise national security if disclosed is classified as RESTRICTED DATA. This definition serves to protect sensitive information and prevent unauthorized access or use that could lead to proliferation or other security risks.

The other options refer to various legislation. The Freedom of Information Act pertains to public access to government documents, the Nuclear Regulatory Commission Act governs the NRC's operations, and the Energy Reorganization Act deals with restructuring the Department of Energy and nuclear project oversight. However, none of these define RESTRICTED DATA in the same context as the Atomic Energy Act does, thus solidifying the choice of the Atomic Energy Act of 1954 as the correct response.