Solution:The Nuclear Non-Proliferation Treaty (NPT: Treaty on the Non-Proliferation of Nuclear Weapons), which entered into force in March 1970, seeks to inhibit the spread of nuclear weapons.
Its all states-parties are classified in two categories Nuclear Weapon States (NWS) consisting of the United States, Russia, China, France, and the United Kingdom -and Non-Nuclear Weapon States (NNWS).
Under the treaty, the five NWS (Nuclear Weapon States) commit to pursuing general and complete disarmament, while the NNWS (Non-Nuclear Weapon States) agree to forgo developing or acquiring nuclear weapons.