第一节 单项填空(共15小题；每小题1分，满分15分)
21．—The floor is dirty．Can anyone clean it?
— I do it all the time．
A．Don't mention it． B．Why you? C．Not sure．D．Not me again．
22．Do not start a book unless you can see from the first few pages that it is you can easily read and understand．
A．that B．one C．the one D．that one
