According to Studies on Voting Preferences and Message Effects, Primacy

According to studies on voting preferences and message effects, primacy effects seem to prevail when we ________ vote for one of the candidates.

A) hear one candidate speak, wait a week, hear the other speak, wait a week, and then
B) hear one candidate speak, hear part of the other candidate's speech, and then
C) hear one candidate speak right after another and then wait a week before we
D) hear one candidate speak, hear a heckler, hear the other candidate speak, and then