American people divide their days into several blocks of time, and plan different activities __21__ different times. American time is “on the dot”(准确地). If something is supposed to happen at eight o'clock, it will begin at eight. Americans value promptness(准时)and may become angry if a person is more than 15 minutes late __22__ a good reason. If you know you are going to be late, call in advance and let someone know. __23__ you arrive late, you should apologize and explain why. Americans arrive __24__ time for doctors' appointments. The doctor may keep you __25__, but if you keep the doctor waiting, you may get a bill with the doctor's time! 21)、 A.for B.waiting C.on D.if E.without 22)、 A.for B.waiting C.on D.if E.without 23)、 A.For B.Waiting C.On D.If E.Without 24)、 A.for B.waiting C.on D.if E.without 25)、 A.for B.waiting C.on D.if E.without