as to 属于复合介词,意思为:至于,关于。
含义及用法:
1、表示涉及某点:as to常放于句中,表示“关于……方面”、“有关……之事”,但为了突出要提及的人或事之时,也可将as to置于句首,以示强调。但只涉及内容,而不涉及讲话人的态度。例如:
(1)His wife,an old teacher,has no complaint as to salary.(2)As to your ability to overfulfil the target,I never had the slightest doubt.
2、用以重提旧事:as to引出的内容都是前文曾经提到过的或者谈话对方都有所了解的,表示“说到”之义。,例如:
(1)As to doing that,I haven't decided yet.
(2)As to the question you raised in your last letter,I think that it is unanswerable.
3、用于提出问题:as to必须位于句中,前面出现的大都是表达某种心理活动的动词,形容词或名词,其后引接出wh-clause或who-to-v结构,表示“在……的问题上”、“就……问题来讲”,所引出的问题都有很强的针对性。例如:
(1)There is some doubt as to whether the proposal is practicable.
(2)I enquired of the clerk as to which documents were needed.