In a modern democracy:
a. all elected officials serve for a certain number of terms then must retire
b. a high school sophomore and a senior citizen may vote at the polls together
c. a us senator votes on immigration law on behalf of your mother through indirect ballot
d. all democracies have a two chamber system of representation
e. we, in the us, live in a direct democracy

The correct answer should be A. all elected officials serve for a certain number of terms then must retire.
Let's use the system of elimination: 
B is incorrect because high school sophomores cannot vote yet (legal age for voting in the US is 18, and sophomores are 16)
C is incorrect because this is done through direct ballot
D is incorrect because there are democracies which have more
E is incorrect because a direct democracy doesn't exist anymore - it existed only in ancient Greece