not...but...如何加从句

所给的例句就是陈述句。再如： They want not your pity but your help. He helped not me but you. Ask not what your country can do for you;ask what you can do for your country. You should pay attention not to what they say but to what they do. but 还可以被直接看作是连接词： No man is too old but he may learn.【but=but that引出的从句有结果含义】【其中的that经常省略】 It never rains but it pours.【but=but that】 There is no rule but has exception.【关系代词】 Not a man but has tears in his eyes.【关系代词】

问得好！省略，概括来讲，都有统一的条件，即【适用文体的限制：口语和非正式文体才经常用省略形式；二正式文体和正式交际场合都不用省略，以示庄重】