The correct answer is A.
On October 15, 1962, Air Force Pilot Richard Heyser was flying a spy plane over Cuba. He took pictures of Russian medium-range missiles. Soviet leader Nikita Khrushchev had asked Cuba President Fidel Castro if he could put them there in May.
The Cuban Missile Crisis was a 13-day confrontation between the USA and the Soviet Union. The US deployed ballistic missiles in Italy and in Turkey and the Soviet Union responded with placing them in Cuba. The missiles in Cuba were seen as a direct treat to the U.S. security.
This confrontation is often considered to be the closest the Cold War came to escalating into a full-scale nuclear war.