21. It is        great shock for all of us to hear        news that three university students lost their lives because of saving others.

A. the£» a   B. I£» a    C. I£» /    D. a£» the

22.         we can't remove our troubles in life for ever£¬ we can leave them behind when we are on vacation.

A. When   B. While    C. Unless      D. Until

23. As he has been well trained£¬ this young man is        to be a teacher.

A. delighted  B. possible    C. qualified    D. unable