题目内容：

   Frank bought a new doorbell, but nobody seemed to notice it. When his friends came, they knocked heavily at the door. Frank was not happy about it.

   One day a friend came to see Frank. He knocked at the door loudly. Frank came to the door, but didn’t open it. He shouted at the visitor from inside. “ I can’t hear you! Please ring the doorbell!”

1.What did Frank buy?

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2.Why wasn’t Frank happy?

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3.Who came to see Frank one day?

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4.Why didn’t Frank open the door?

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5.Did Frank hear the knock?

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