When did Castro announce his alliance that caused the U.S. to break ties with Cuba?

The correct answer is that Castro announced his alliance with the Soviet Union in 1961, which was a significant turning point in U.S.-Cuba relations. This alliance marked the strengthening of ties between Fidel Castro's government and the Soviet Union, especially during the context of the Cold War. The U.S., alarmed by the prospect of a communist ally so close to its shores, responded by breaking diplomatic ties with Cuba. This event escalated tensions, leading to events like the Bay of Pigs invasion and the Cuban Missile Crisis.

The other alliances mentioned, such as those with Honduras, Costa Rica, and Nicaragua, did not play the same pivotal role in affecting U.S.-Cuban relations during this period. They lack the critical geopolitical implications that Castro's relationship with the Soviet Union introduced, making option B the most relevant and impactful choice in the context of the question.