Question

the closest the world came to war during the cold war was when the soviet union placed missiles on the caribbean island of aruba puerto rico cuba saint thomas

Explanation:

This refers to the Cuban Missile Crisis, a 1962 Cold War event where the Soviet Union deployed nuclear missiles in Cuba, bringing the U.S. and USSR to the brink of nuclear war. The other listed islands were not the site of this critical missile placement.

Answer:

Cuba