题目内容：

clever as he is, ___he doesn't work hard enough to pass the test.
A but B however C so D yet

优质解答

这时由as引导的让步状语从句,但是此句有though的含义,所以后面就不应该有but；however作副词时前后都应该有逗号,做连词时不能直接引导一个完整句子；此举是转折之意,不该用so；所以选D,yet.