First, let's be sure we understand the question itself. You are asked what the phrase "gaining disproportionately from awards of damages" (lines 18-19) is intended to mean.
Returning to the relevant section of the passage, we can see that the phrase is used in the context of commentary re: avoiding lawyers from benefiting disproportionately from cases than they should (i.e., taking more of a damages award), at the expense of their clients (whose "just compensation" may thus be "eroded").
Answer choice (B) is correct: the phrase in question is intended to mean that lawyers should not receive "a higher portion of the total amount awarded in damages than is reasonable compensation for the professional services rendered and the amount of risk assumed."
Answer choice (A) can be eliminated because, in the context of the passage, the phrase is not about "payment that is of greater monetary value than the legal services rendered." Answer choice (C) can be eliminated because of the words "client considers fair" (this isn't just about what the client considers fair). Answer choice (D) is irrelevant (in contingency cases, a lawyer receives no payment if the client's case is unsuccessful). Answer choice (E) is similar to answer choice (C) - this is not about the judge or jury would do.
Hope this helps. Please let us know if you have any additional questions.