as在開頭引導什么從句

　　As還可引導時間狀語從句,“當,隨著”：

　　例如：As the weather is colder and colder,the leaves of the tree is less and less.

　　As還可引導方式狀語從句,“按照”：

　　例如：You must do the work as I have told you.

　　As還可引導讓步狀語從句.“盡管”。但是注意,as引導方式狀語從句時從句必須倒裝。而且這種倒裝和一般的倒裝不一樣。as從句的倒裝一般是把從句的表語或作狀語的副詞提到as之前,（如果表語是一個帶有不定冠詞a或an的單數名詞,倒裝后a或an必須省略)。

　　例如：Though he is a little boy,he knows a lot.如果變成由AS引導,就必須變成：

　　Little boy as he is,he knows a lot.

　　Though he works hard,he never succeed.

　　可變為 Hard as he works,he never succeed.