however引导让步状语从句时,相当于no matter how,后面跟形容词或副词;as引导让步

however引导让步状语从句时，相当于no matter how，后面跟形容词或副词；as引导让步状语从句时，用倒装语序，即把作状语的副词或作表语的形容词或名词提前，而且如果作表语的是单数名词，前面不加冠词，也可以把谓语动词部分的实义动词提前。
[误] As hard he works,he can’t catch up with his classmates.
[正] However hard he works,he can’t catch up with his classmates.

问：为何As hard he works,是错的，根据上面讲的，as引导让步状语从句时，用倒装语序，即把作状语的副词或作表语的形容词或名词提前，这些都满足呀

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②as引导让步状语从句时一般放在主句之前，须用倒装圆返悉语序。从句中的表语世笑、状语或动词原形置于句首，若表语橘乎为名词，前置时要省略冠词
Child as he is, he knows a lot. (=Though / Although he is a child, he knows a lot.)

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as表示虽然的时候，需要倒装， as不能穗消位于猜姿知句首。册帆应该是 ：Hard as he works,....

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