四、单项选择。（共15分，每小题1分）
从下列各题所给的A、B、C、D四个选项中，选择可以填入空白处的最佳选项，将其代号填在答题卡相应的题号后。
21. —The pet dog is very nice. Is it _______?
—Yes, but I’ll give it to Lucy as a birthday present.
A. you B. your C. yours D. mine
22. John usually does outdoor activities _____ Sunday.
A. on B. in C. at D. of
