Why is A not the answer??

Correction to my post: Will you please explain why A cannot be the answer??

(A) might probably be a possibility had the first sentence been the Conclusion, but if it is understood that the Conclusion is the final sentence, it becomes clear that the question stem is describing a premise rather than a phenomenon.

@Kyra @student is basically right - I would add that even if the first sentence had been the conclusion, the claim that “people tend not to reelect inactive politicians” is not really /explained/ by the fact that people’s political behavior frequently does not match their rhetoric, as answer A requires. Nor does it /explain/ the actual conclusion — that voters often reelect politicians whose behavior they resent. Instead, that claim is one link in the chain of the argument — in other words, it is a premise. And it is a premise that supports the final conclusion, as answer B correctly states. I hope that helps! Let us know if you have further questions.