3.由as, that, though引导的特殊让步状语从句结构：

在正式文体或文学作品中，为了强调让步的含义，可用as引导让步从句。但as一般不置于句首，而将从句中的表语或状语置于句首。（though, that与as一样，也可以用于这种结构），如下面几种情况： ① 表语的倒装： Tired as he was, he still went on with his work. Difficult though the task was, they managed to accomplish it in time. ② 状语的倒装：（这时不可在状语之前加very, much等修饰语） Much as he likes the bike, he doesn’t want to buy it. Hard as I studied, I could not catch up with them. ③ 谓语动词的倒装： Try as he would, he could not remember a word of it. (= No matter how he would try …) Search as they would, they could find nothing in the room.