二、单项选择(共15小题；每小题l分，满分l5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，填在题前括号内。
( )21. This is________old map, but it's still useful.
A. a B. an C. the D. /
( )22. Mrs Wang has taught_______geography for two years and she teaches very well.
A. our B. we C us D. ours
