第一节：单项填空（共15小题；每小题1分，满分15分）
从下列每题所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑。
21. As is known to all, pandas are _________ native to China, that is, China is ________ home to pandas.
A. the; the B. the;/ C. /; the D. /;/
22. I am _______ about what I say because careless remarks are likely to hurt others’ feelings.
A. enthusiastic B. concerned C. doubtful D. cautious
