______into the accident, the police concluded that both of the drivers were responsible for it．
| A．Having looked | B．Looked | C．To look | D．To be looking |
Professor John will give us a lecture on how to learn English, but when and where _____ yet.
| A．hasn’t been decided | B．haven’t been decided |
| C．isn’t decided | D．aren’t decided |
Having taken our seats, _______.
| A．the professor began the lecture |
| B．the lecture began in no time |
| C．we were attracted by the lecture immediately |
| D．the bell announced the beginning of the lecture |
Do you think the reason _______ he gave is believable?
| A．when | B．why | C．what | D．which |
Thank you for your timely help, otherwise we _______ in great trouble now.
| A．are | B．would have been |
| C．would be | D．were |
_______ apple four hundred years ago led to the law of gravity while _______ apple designed by Steve Jobs has changed our life greatly.
| A．The; an | B．An; an |
| C．An; the | D．The; 不填 |