What information is missing from the table that could help someone draw the most accurate conclusion about voter turnout in primaries and general elections?
The correct answer is letter c: the percentage of Democratic primary voters because you want to know the percentage of citizens that vote Democrats or Republicans to compare them.
Letter A is not necessary to have this information in the table because this chart is a general one, and is not relevant the year in which it is carried out (you can use this table at any time).
Letter B is not relevant information because citizens know which are the candidates, and what you are interested in obtaining is the percentage of people that vote for Democrats or Republicans, not the candidates.
Letter D is not relevant information because you have the column "state" in which you can describe each state.