Virtually all eligible voters who took part in a recent survey of

IMO B

B) Only eligible voters who did not choose to vote in the most recent election were included in the recent survey.

This justifies the paradox.

KarishmaB, GMATNinja, AndrewN
OA is B, but B should be eliminated as it needs further assumption that those eligible voters who did not took part in survey did not agree with those who took part. Then only they could have took part in election.
Whereas A says Whereas A says that even though candidates are corrupt but people had to vote atleast 1 candidate

Observations:
A survey was conducted.
Virtually all eligible voters who took part in the survey said that candidates are incompetent or corrupt (or both), so it is a waste of time to vote.
Yet nearly 80% of eligible voters chose to vote in the most recent Artesianan election.

So as per the survey, almost everyone felt that it is a waste of time to vote (i.e. it is better to not vote) but still 80% people voted.

What can help resolve the paradox? If the people in the survey were almost all from the 20% set of people who did not vote then the paradox is resolved. The survey gave the opinion of a certain set of people and that set believed that it is a waste of time to vote. But it did not reflect the opinion of everyone. Normally, we expect a sample to give us information about the entire population but for that, the sample should be unbiased. Basically we are saying that there was a selection bias in the survey and that does explain the observations. It all makes sense then.

B) Only eligible voters who did not choose to vote in the most recent election were included in the recent survey.

That is why option (B) works.
rickyric395 - we don't have to ASSUME that the people who did not participate in the survey did not agree that voting is a waste of time. We KNOW that they did not think that voting is a waste of time. That is why they went and voted.
Option (B) tells us how we could have observed what we did - that in the survey most people said that voting is a waste of time but still 80% people voted. Because the survey participants all belonged to the 20% group.


E) Those voters who took part in the recent survey acted in accordance with their beliefs by refusing to waste time voting in the recent elections.

The statement should say "eligible voters," not voters because these people did not vote - we are told. But it doesn't change the fact that this option does not explain the paradox. It only supports the paradoxical situation.
The eligible voters who took part in the survey acted according to their beliefs. So this tells us that these people did not go to vote. Now we are still wondering that how come 80% people voted then? If people acted according to their beliefs and if it seems that most people felt that voting is a waste of time, then from where did these 80% voters come?

Answer (B)

KarishmaB , Can you please share your thought on option A ?

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In option (A), "compelled" does not mean that someone forced them to vote. We are given that they "chose" to vote. It means that the ones who chose to vote had no option but to vote for one of the incompetent or corrupt candidates (because all were like that).
Does it explain why 80% people took out the time to vote? No. 

But if we find out that the rest 20% people who thought that it was a waste of time to vote were the ones participating in the survey, then the survey result and the election tourout makes sense. These 80% did not think that it is a waste of time to vote and they did not participate in the survey either.