The correct answer is C) "personal appeals".
When a speaker is searching for support in an audience it is very effective to refer to the friendship and loyalty that this audience has had towards the speaker until that moment and ask once again for their support regarding the upcoming decision-making process. This is a technique which political candidates use quite often during political meetings in the days prior to the election day. Proposals and the appliance of techniques such as exchange are no longer effective with such a tight deadline, leaving the personal appeal as the best way to reach an audience's emotions and get the necessary buy-in.