—Look at these tracks. It __________ be a wolf.
—It needn't be. It be a fox.
| A．must ; could | B．may ; might |
| C．need ; must | D．could ; need |
_____ he promised that he wouldn’t be late，he didn’t arrive until the end of the party．
| A．Since | B．Although |
| C．Because | D．Until |
Since the new speed limits ______，the number of accidents in the area has fallen strikingly．
| A．were introduced | B．introduced |
| C．have been introduced | D．have introduced |
When Kerry and Sam met again two years later，each was pleased to see ____．
| A．the other | B．others |
| C．another | D．other |
Tony couldn’t remember ______he had turned off the computer before he left the office．
| A．that | B．where |
| C．when | D．whether |
All of us are pleased to see the problem ______ so quickly．
| A．solve | B．solving |
| C．to solve | D．solved |