【问】 On no account______ be removed from the library.
 A. reference books may B. may reference books
 C. reference books cannot D. reference books
 我不明白这里为什么只能选B(may reference books)，而不能选A(reference booksmay)。
 【答】 当否定词never，not，no引出的否定成分位于句首时，在正式语体里，必须采用主谓语倒装的语序，即助动词+主语+实义动词。
 1. On no account must you accept any money if he offers you.
 如果他给你钱，你绝不要接受。
 2. Not a word would he say. (CGEL)
 他一句话也不愿意说。
 3. Never again did Alfred E. Smith seriously seek political office after his 1928 defeat forthe presidency.
 艾尔弗雷德·伊·史密斯自从1928年竞选总统失败之后，就再没有认真地谋求政府官职。
 4. Under no circumstances must the door left unlocked.
 在任何情况下都不允许不锁门。
 5. To no one will they admit their guilt. (CGEL)
 他们对任何人都不会承认有罪。
 6. Not until Madame Curie discovered radium did people have an idea of radioactivity.(EPT)
 直到居里夫人发现了镭，人们才知道什么是辐射。
 7. Not always can people do what they want to. (IME)
 人们并不是总能做他们想做的事情。
 8. Not a single book had he read that month. (CGEL)
 他那个月一本书也没读。
 9. In no circumstances must this door be left open. (CGEL)
 在任何情况下都不允许这扇门开着。
 10. No longer are they staying with us. (CGEL)
 他们不再和我们住在一起了。
 (参见Never did we)