Primaries only allow registered members of a political party to vote to select that party's candidates, whereas primaries allow all registered voters to choose which party's primary they will participate in.

I am pretty sure that correct statement looks like this: Presidential primaries only allow registered members of a political party to vote to select that party's candidates, whereas open primaries allow all registered voters to choose which party's primary they will participate in. It's tricky question, but according to its definitions, the answer is correct.

The answer is c. good luck : )