______alittlemoretimetothink,hemighthaveactedmoresensibly.
A.If he tookB.If he has takenC.had he takenD.Should he take在线课程C
解析：
考查在条件句中与过去事实相反的虚拟语气。其结构为：if+主语+had done,主语+would/could/might+have done ,省略if要倒装，had往前提，故选C。