第二部分 英语知识运用(共两节， 满分45分)
第一节 单项填空(共15小题；每小题1分，满分15分)
从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
21. Obama made _______ history by being elected as ________ first black president of the US.
A. 不填；the B. a; the C. a; a D. the; a
22. Many citizens urged their government to take measures to _______ their carbon emission to reduce greenhouse effects.
A. cut off B. cut up
C. cut out D. cut down
23. --How was your weekend, Rose?
--Awful! This was the first time I ________ alone at home, bored to death.
A. had left B. had been left
C. have been left D. have been leaving
