Jim took my book by mistake.He ought ___ the yellow one.
| A．to take | B．to have taken | C．take | D．have taken |
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 |
One more month，______these baby birds will fly out of their nest.
| A．or | B．and | C．but | D．otherwise |