Critical Reasoning

2,500 individuals of voting age were polled and asked where they stood on the political spectrum. 78% of these individuals described themselves as "moderate" in their political views; however, in the national elections that most closely preceded and followed the poll, over half of the individuals polled voted for candidates far to one end of the political spectrum. It follows that these individuals did not accurately describe their political views.

Which of the following is an assumption on which the above argument relies?

a. Individuals always characterize themselves in keeping with their actual political views.
b. There were no moderate candidates in the national elections preceding and following the poll.
c. Voters with moderate political views will not vote for candidates who do not express moderate political views.
d. Voters can be highly fickle, changing their political views in a relatively short period of time.
e.Many of the polled individuals did not understand what a moderate political view is, and so misdescribed themselves.

oa is c

I have been confronted with this one a couple of times and each time I haven't understood the official explanation. Can someone just explain this one in very layman terms?