Answer: C. The United States discovered nuclear missiles being stationed in Cuba.
Explanation:
There is no correspondence attached but option C is most probably the answer because it is the only factual option there.
When the United States found out that nuclear missiles were being positioned in Cuba which was so close to the American mainland, it sparked the Cuban Missile Crisis which saw the two Superpowers almost go to war until an agreement was reached to withdraw missiles from Cuba and Turkey.
