Although the causes of cancer_____, we do not yet have any practical way to prevent it.
| A．are being uncovered | B．have been uncovering |
| C．are uncovering | D．have uncovered |
If I were in ______ position of the headmaster, I would make every effort to bring ______ end to cheating in exams.
| A．/; the | B．a; the | C．a ; an | D．the; an |
----Have you worked in this company for a long time?
---- Yes, since I _________ from the college.
| A．has graduated | B．graduates |
| C．had graduated | D．graduated |
Completely ______with delicious food, Tom wanted to stay there for another two days.
| A．based | B．crazy | C．obsessed | D．being obsessed |
----Tang is absent today.
---- _________ He is never late for work.
| A．Go on. | B．How come? | C．Why not? | D．Never mind |
Don’t look down upon the ugly little worm. In a few weeks , it ________into a beautiful big butterfly.
| A．transforms | B．would transform | C．have transformed | D．will transform. |