What is the difference between a river valley civilization and an empire

1) the answer is b

senators serve a six-year term; representatives serve a two-year term, making them more responsive to (and responsible for) voter confidence.

2) the answer is d

to serve as president, one must:   -be a natural-born u.s. citizen of the united states;   be at least thirty-five years old;   be a resident in the united states for at least fourteen years.

3) the answer is a

ella,because it is constitutionally eligible

4) the answer is c: the u.s president

it increase by 12% a year from 1812-1820