Which of the Following Would Be an Example of Nuclear

Which of the following would be an example of nuclear proliferation?

A) Dismantling of nuclear weapons by the United States and the Soviet Union
B) Diplomacy used between countries that have nuclear weapons
C) Creation of huge nuclear arsenals during the Cold War by the United States and the Soviet Union
D) Spread of nuclear weapons to countries that do not currently possess them
E) Failure to determine an accurate number of nuclear warheads per nation