Only after the second tower of the World Trade Centre          did people know it was not an accident, but an attack of some kind．

 A．had hit         B．did fall        C．was hit        D．was fallen

Only after the second tower of the World Trade Centre____ did people know it was not an accident, but an attack of some kind.

A. had hit　　　 B. did fall　　 C. was hit　　 D. was fallen?

Only after the second tower of the World Trade Centre 　　　　 did people know it was not an accident, but an attack of some kind.

A. had hit　　 B. did fall

C. was hit　　 D. was fallen

Only after 　　　　　did people know it was not an accident, but an attack of some kind.

　 A. the second tower of the World Trade Centre was hit

B. did the second tower of the World Trade Centre fall

C. was the second tower of the World Trade Centre hit

D. the second tower of the World Trade Centre was fallen