答案A. 这是一个倒装问题。当否定词语置于句首以表示强调时，其句中的主谓须用倒装结构。 这些否定词包括no, little, hardly, seldom, never, not only, not until等。本题的正常语序是 Smoking is permitted in the meeting-room at no time.

2） Not until the early years of the 19th century ___ what heat is.

A. man did know　 B. man know　 C. didnt man know　 D. did man know

答案D.　 看到Not until...的句型，我们知道为一倒装句，答案在C，D 中选一个。

改写为正常语序为，Man did not know what heat is until the early years of the 19th. 现在将not提前，后面就不能再用否定了,否则意思就变了。

3 以否定词开头作部分倒装

如 Not only...but also, Hardly/Scarcely...when, No sooner... than

Not only did he refuse the gift, he also severely criticized the sender.

Hardly had she gone out when a student came to visit her.

No sooner had she gone out than a student came to visit her.

典型例题

No sooner___ than it began to rain heavily.

A. the game began　　　　　 B.　has the game begun

C. did the game begin　　　 D.　had the game begun

答案D. 以具有否定意义的副词放在句首时，一般采用倒装句(谓语