--Who______ it be that is knocking at the door?
--It ______ be Father, but I’m not sure.
| A．can; may | B．can; must |
| C．must; can | D．may; must |
It was not until she failed in the exam ______she realized the importance of study.
| A．when | B．did | C．and | D．that |
________at the restaurant with a wide variety of dishes served before, Bob didn’t want to eat there again.
| A．Having eaten | B．To eat | C．Eat | D．Eating |
He was about to tell me the secret ______ someone patted him on the shoulder.
| A．as | B．until | C．when | D．while |
I ________ to visit you later that day, but I had to phone and cancel.
| A．come | B．came | C．am coming | D．was coming |
When we saw the road ______ with snow, we decided to spend the holiday at home.
| A．cover | B．to cover | C．covering | D．covered |