The correct answer is C) The two nations wanted to best one another in the development and stockpiling of nuclear weapons, which drove the competition between them.
This aforementioned competition between the US and Soviet Union was a significant part of the Cold War era. This era of the Cold War saw the United States and Soviet Union compete for global power and influence. Considering these two countries were somewhat hostile towards each other during this time, both wanted to be ready in case actual fighting broke out. This resulted in the arms race, which was essentially a race to see who could possess the most military weapons/military power.