A student was going to spend his holiday in a cool mountain village. That evening he stayed at an inn (小旅馆) near the railway station (火车站). Before going to bed, he went to the boss of the inn and said, "Excuse me, sir. Will you please wake me up at a quarter to five tomorrow morning? I'll take the five o'clock train."
"Oh, sorry, sir," the boss said in a hurry, "I'm afraid I can't. I won't be able to get up so early." The student was disappointed. When he began to return to his room, be stopped and asked, "Have you got an alarm-clock (闹钟)? Maybe it can help me."
"Wait a minute, then." The boss said and brought out an alarm-clock. "Here you are, sir." "Thank you very much." The student said happily. But he found it was rusty (锈的) when he had a look at it. And it sometimes worked and sometimes didn't. He asked, "Will it ring in time?" "I don't know, either." said the boss, "But it doesn't matter. You just give it a good shake at a quarter to five. And it will ring on time."