The correct answer is D) The United States and Soviet Union.
In October of 1962, the US discovered that the Soviet Union had put missiles in Cuba. This was worrisome for the United States, since Cuba was only 90 miles away from Florida. This meant that the Soviet Union could attack America very quickly since Cuba was so close.
Over the course of the next 13 days, the US and Soviet Union came extremely close to all out nuclear warfare. There was constant confrontation and communication between US president John K Kennedy and Soviet leader Nikkita Khruschev. Ultimately, both sides came to a peaceful solution to this problem.