PART TWO: LANGUAGE KNOWLEDGE （30 points）
Section A（10 points）
Directions: Beneath each of the following sentences there are 4 choices marked A, B, C and D. Choose one answer that best completes the sentence.
21. When I called at his home the other day, I found him sitting on an armchair,________ in his hands.
A. buried his head B. burying his head
C. his head burying D. his head to be buried
22. Mr. White, along with his assistants, ______ on the project day and night to meet the deadline.
A. work B. working C. is working D. are working
23. All possible means ______ been taken to prevent the river _______.
A. have; polluting B. has; polluted C. has; from polluted D. have; being polluted
