The correct answer is C.
In the Cold War era, the US had adopted the containment strategy that aimed to stop the expansion of communism and of the influence of the URSS throughout the world.
After the sucess of the Cuban Revolution in 1959, leaded by Fidel Castro, a communist goverment and economic system was established in the island. Hence Cuba, which had been a US ally and a country under its influence, became a communist nation on the enemy's side. Economic and political relationships between the US and Cuba were totally broken and intense tensions emerged on the region.