as、than、but用作关系代词,在从句中本身即作主语时,后面一般就不加主语,如:The two brothers were satisfied with this decision, as was agreed beforehand. 两兄弟对这个决定都满意,它事先已经他们同意了。(关系代词as在从句中用作主语,其先行词是this decision)He was a foreigner, as I knew from his accent. 他是个外国人,我是从他的口音知道的。(关系代词as在从句中用作宾语,其先行词是前面的整个句子)I never heard such stories as he tells. 我从未听过他讲的这类故事。(关系代词as与指示代词such连用,在从句中用作宾语,其先行词是such stories)Her attitude to him was quite the same as it had always been. 她对他的态度同她惯常的态度完全一样。(关系代词as与指示代词same连用,在从句中用作表语,其先行词是same)You spent more money than was intended to be spent. 你花的钱超过了预定的数额。(关系代词than在从句中用作主语,其先行词是money)There are very few but admire his talents. 很少人不赞赏他的才干的。(关系代词but在从句中用作主语,其先行词是few,but=who don’t)