21. Not everybody has realized what ______important part the balance of ______ nature plays in their life.
A. an; / B. an; the C. /;the D. the; the
22. The player is under good treatment and the ______are that he`ll recover from his injury soon.
A. conditions B. opportunities C. chances D. occasions
23. The school rules state that no student ______be allowed into the school-yard by bicycle.
A. will B. should C. shall D. would
