The students were ________ over the ________ problem，listening to the teacher with a ________ expression on their faces.
| A．puzzled；puzzling；puzzling | B．puzzled；puzzling；puzzled |
| C．puzzling；puzzling；puzzled | D．puzzling；puzzled；puzzling |
----Is it my age __________ the boss minds?
----I’m afraid not. He will consider __________ necessary to have an experienced assistant.
| A．which; it | B．that; it | C．which; that | D．that; that |
Tony, would you go and see if Sam has any difficulty __________ his tape recorder?
| A．to fix | B．fixing | C．for fixing | D．fix |
Can you think of some cases __________drivers obviously knew the traffic rules but did not obey them.
| A．which | B．as | C．where | D．that |
The teacher highly recommended that I ___________ more to improve my English.
| A．would practice | B．could practice | C．practice | D．practiced |
Liu Xiang achieved his __________ to become the first man to cover the 110-meter hurdles in less than 12.91 seconds.
| A．ambition | B．graduation | C．assistance | D．encouragement |