Soon after the Second World War had ended, several disagreements emerged among the allied powers of the war, namely the United States of America, the United Kingdom, and the Soviet Union. Especially, they failed to reach an agreement on the post-war international order. The Soviet Union started to dominate Eastern Europe by imposing socialist ideology on the regional powers and expanded its sphere of influence. This was opposed, however, by the Western powers, including the US. As a result, the US decided to form an alliance to minimize the Soviet influence in Europe and get prepared for a possible attack by the socialist/communist states. Therefore, the correct option is E.