—Who______ it be that is knocking at the door?
—It ______ be Father, but I’m not sure.
| A．can; must | B．can; may | C．must; can | D．may; must |
After completing and signing it, please return the form to us in the envelope ___.
| A．providing |
| B．provided |
| C．having provided |
| D．provide |
When ___for his views about his teaching job, Philip said he found it very interesting and rewarding.
| A．asking |
| B．asked |
| C．having asked |
| D．to be asked |
The professor spoke very clearly to make his speech ___.
| A．understood |
| B．understand |
| C．understanding |
| D．to understand |
Her ___ look suggested that she was completely ___.
| A．puzzled; confused |
| B．puzzling; confusing |
| C．puzzled; coufusing |
| D．puzzling; confused |
“Bill, keep the things ___ here secret,”said the manager after meeting.
| A．discussed |
| B．being discussed |
| C．to be discussed |
| D．having been discussed |