Richard Nixon was the first president to ever resign from the presidency. He did so so he could avoid being the first president to ever be impeached.
C. FDR believed that the federal government should take an active role in the economy; Hoover didn't.
President Herbert Hoover is what we call a sitting duck president which means he didn't do anything and believed in a philosophy called "Rugged Individualism". Rugged individualism basically means it's every man for himself and Hoover felt that Americans should figure their issues out by themselves and not rely on the government to help them out.
Actions that should be preformed by all citizens but are not required by the law are called FUNDAMENTAL DUTIES
C: Because of low pay, many men only enlisted for three months. I hope this helps :)