It was not until all the fish in the pond died that________ the situation was serious.
| A．did he realize | B．he realized |
| C．he had realized | D．had he realized |
The Grand Theatre is located on one corner of________ is called the People's Square.
| A．which | B．what | C．the place | D．that |
Better not call the manager between 8 and 9 this evening, for he_________ an important meeting then.
| A．will have | B．would have | C．will be having | D．will have had |
Listening to peaceful music. as well as taking exercise,___________ a lot in relieving people 's sad emotions.
| A．help | B．helped | C．helps | D．are helping |
The man__________has made up his mind to win will never say "impossible".
| A．whom | B．when | C．which | D．who |
Only when___________ according to the directions can the medicine be quite effective.
| A．taking | B．taken | C．being taken | D．having been taken |