The depression didn't reach the USSR because the USSR did not have a capitalist government. It also didn't have a stock exchange and didn't trade with any capitalist governments. The USSR was also very isolated because of communism.
The answer is D. HPV because there are no cures for it but many of the small infections go away on their own.
Imperalism by definition is the policy of expanding your countries power through military or diplomatic means. And expanding your country to another continent, with many resources untapped and people of inferior technology means you could easily conquer and expand
