Answer:
A. the us using nuclear weapons to end ww2
Step-by-step explanation:
at the time the US and USSR were the main super powers and germans had been defeated and the us use the bombs on Japan. The US and USSR had tensions but didnt want to start another war, with the US showing off their atomic bombs the Soviets felt threatened and had to one up them. which started the cold war and they just had to keep one upping each other.