Although the United States and the Former Soviet Union Had

Although the United States and the former Soviet Union had been allies during World War II, by the late 1940s they became engaged in a struggle that saw both build up their militaries, develop the ability to destroy each other completely through nuclear weapons, and fund and fight with opposing sides in conflicts worldwide.It became known as the "Cold War," however, because:

A) the two countries never directly engaged in all-out war with each other, with the full force of their militaries.
B) leaders of the countries, despite coming to the brink of war many times, refused to engage with each other in diplomatic talks.
C) the United States and the Soviet Union technically remained allies, despite their evident hostility to each other.
D) the two countries never formally declared war on each other.