Not until they left school how much their teachers loved them and helped them.
| A．they realized | B．did they realized |
| C．they would realized | D．had they realized |
Work hard at your lessons, ______ you’ll fail the exams again.
| A．and | B．but | C．or | D．which |
We’ll never forget the days ______ we lived in the country.
| A．when | B．where | C．which | D．不填 |
I am sorry I didn’t hear you clearly. _____you repeat it please?
| A．Could | B．Must | C．May | D．Need |
—I regret____ to tell ____you that John has been fired.
—I can hardly believe my ears. He is such a fine worker.
| A．telling | B．having told | C．to tell | D．to have told |
He failed the mid-term examination and only then________how much time he had wasted.
| A．he realized | B．did he realize |
| C．he had realized | D．had he realized |