One of the biggest problems was at the national government had no power to impose taxes. to avoid any perception of "taxation without representation," the Articles of Confederation allowed only state government to levy taxes. To pay for it's expenses, the national government had to request money from the states.
The cold war ended. Nixon was not impeached but resigned before he could get impeached. By process of elimination it is c or d. I am not 100% sure. Hope this helps.
