Once __________, the play was well received by the public.
| A．perform | B．performing |
| C．performed | D．to perform |
----Hello, may I have an appointment with the headmaster?
---_____.
| A．Sorry, he is busy at the moment | B．No, you can’t |
| C．Certainly. Wait a minute, please | D．Let me see |
He is ready to help others, seldom, ______ refusing them when they turn to him.
| A．if never | B．if ever | C．if not | D．if any |
Robert is said ______ abroad, but I don’t know which country he studied in.
| A．to have studied | B．to study | C．to be studying | D．to have been studying |
I can remember very few ______ when he had to cancel his plans because of poor health.
| A．situations | B．conditions | C．occasions | D．circumstances |
He hurried to the booking office only ______ that all the tickets had been sold out.
| A．to tell | B．to be told | C．telling | D．told |