Which treaty, signed in 1963, prohibited atmospheric nuclear tests?

• A. Partial Test Ban Treaty
• B. Nuclear Non-Proliferation Treaty
• C. Comprehensive Nuclear-Test-Ban Treaty
• D. Limited Test Ban Treaty

Answer: (A)

The idea tested here is understanding which agreement limited where nuclear explosions could be conducted. The treaty signed in 1963 that prohibited atmospheric nuclear tests is the Partial Test Ban Treaty, also known as the Limited Test Ban Treaty. It specifically bans nuclear explosions in the atmosphere, in outer space, and underwater, leaving underground testing allowed. This step reflected a shared concern about radioactive fallout and helped curb environmental and health risks while letting the major powers continue to study and develop their arsenals. It was signed by the United States, the United Kingdom, and the Soviet Union and laid groundwork for later efforts to ban all testing, like the Comprehensive Nuclear-Test-Ban Treaty, though that broader ban came much later. The other options address different aims or timelines (nonproliferation broadly, or a total ban), so they don’t match the 1963 atmospheric prohibition you’re asked about.