--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 |
No one imagined that the apparently _____ businessman was really a criminal.
| A．respectful | B．respectable | C．respective | D．respected |
We won't know whether it will be successful. We won't know whether there will be good _____.
| A．ends | B．results | C．effects | D．causes |
The government placed _____ on the numbers of foreign cars that could be imported.
| A．limitations | B．restraint |
| C．requirements | D．restrictions |
He ate what he could, and gave the _____ of the food to the birds.
| A．remain | B．uneaten | C．rest | D．part |
Mary had taken _____ to see that her guests had everything that they could possibly want.
| A．efforts | B．pains | C．attempts | D．endeavors |