The correct answer is (A). To make the right choice here, you must be able to define the words, of course, and in the case of choice (A), that demands a fairly big vocabulary. So one way to succeed at a question like this is to beef up your vocabulary! If you don't know the meaning of all the words, you can rule out as many wrong answers as possible by focusing on the ones you do know the meaning of.
This sentence states that the person is "vile" meaning
loathsome. This person would be likely to promote or encourage wickedness and to tell lies.
You know "betray" would imply the person is against wickedness rather than encouraging it, so you can rule out (B).
To "thwart" wickedness would be to stop it instead of encourage it, so you can rule out (D) as well.
"Decry" means to speak out against; again, this is not encouraging wickedness so you can rule out (E) as well.
You are left with choices (A) and (C). Let's look at the second word now. "Purveyor" means
one who promulgates something which would imply the person spreads lies. (A) works. But let's look at (C) before piocking a final answer.
"Disparager" means to belittle or speak negatively of which would imply the person is against lies. So you can rule out (C).
