Concept:The correct structure for comparison is "not so much ... as", not "not so much ... but".Explanation:The sentence uses "not so much ... but", which is incorrect.The phrase "not so much X as Y" properly compares two qualities, giving weight to Y.Here, X is "his meanness" and Y is "his dishonesty"."As" is the correct word to introduce the second part of the comparison."But" shows contrast, not comparison, so it is wrong.Thus, "but for" should be replaced with "as for".Option (a) fixes the error.Answer:Option (a) as for.