Answer:
The United States came to power because it led the allied offense in Western Europe against Nazi Germany, and in the Pacific against Imperial Japan.
The war effort also lifted the U.S. out of the Great Depression, and helped the country develop its industry and military even more, at the time that its main competitors were trying to recover from the effects of the war (Germany, France, Britain, Italy, Japan).
The Soviet Union came to power in a similar manner. It led the allied offense against Nazi Germany in Eastern Europe, and it took control of the Eastern European countries. The war also helped the Soviets developed its military and industry, and they had scientific achievements that were on par with those of the United States.
The social structure of ancient China evolved over several centuries, likely solidifying sometime in either the second or third century A.D. The social structure was very rigid; there was virtually no possibility of upward (or even downward) mobility. In other words, if your father was a farmer, chances were you were going to be a farmer, too. The genders were not equal in ancient Chinese society either; women were largely domestic creatures, and even aristocratic women were not allowed to attend school. This social structure was reinforced by the revered Chinese thinker, Confucius, who claimed that social structure and rigid order was important if one wanted a peaceful kingdom and a happy society.
It should be mentioned that the one occupation which existed outside the realm of ancient Chinese social structure was the emperor and the royal family. The emperor was often considered ordained by god in ancient Chinese society and, therefore, he did not have to answer to any humans on earth. He expected complete obedience from his subjects and had total control over military affairs.
I would say that C is correct