Section A (15 points)

Directions: Beneath each of the following sentences there are four choices marked A, B, C and D. Choose one answer that best complete the sentence.

21. The natural disasters in 2008 were _______ challenge for our nation, which urged _______ country’s leading scientists to carry out international cooperation to make disaster prevention.

       A. the; /                        B. a; /                    C. /; the                 D. a; the

22. After fighting against the snowstorm, the young men returned home, _________.

A. safe but exhausted                   B. safety and exhausted

C. safely but exhausting                D. safe and exhausting