In a closed primary
a. only declared party members may vote.
b. all qualified voters may vote.
c. voters must vote a split ticket.
d. voters must complete separate ballots for both parties.

In a closed primary, only declared party members may vote. The advantage of having a closed primary is that it prevents one party from raiding the other primary in the hopes of nominating weaker candidates in the other party.

The answer would be letter A.

One key element is humour! the man probably represents a politician or worker!