问题 填空题

传统的集合运算都是 ______ 。

答案

参考答案:二目运算

解析:

[分析]: 传统的集合运算将关系看成是元组的集合,其运算是从关系的“水平”方向,即行的角度来进行的,包括并、交、差、广义笛卡尔积等,都是二目运算。

阅读理解

阅读下面短文,根据要求完成下列各题。

It was December 25. Marie, a 13-year-old Australian girl, was happy. It was Christmas, and Marie's mother was making a special cake. She put four small coins into the cake,  and then she baked (烤) it. The four coins were for good luck. After dinner Marie and her family ate the cake. They found three coins in the cake and put them on the table. Where was the fourth coin? It was missing, but Marie's mother didn't notice.

After Christmas, Marie got sick. She coughed, and she couldn’t speak. After six weeks she felt better, but she still couldn't speak. Marie's parents took her to hospital. Doctors at the hospital looked her over, and then said, "We are sorry, but we can't help her." For 12 years Marie didn't speak. She grew up, she got a job, and she got married. But she never spoke. One day,  when Marie was 25 years old,  she got a sore throat ( 嗓子疼 ) at work. She began to cough. She coughed up something small and black. What was it? Marie didn't know. She took it to the hospital. A doctor at the hospital said, "This is a coin!" The doctor told Marie, "I think you can speak again." Marie went to a special doctor, and soon she could talk.

根据上面短文的内容回答问题。

小题1:What did Marie's mother make at Christmas?

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小题2:What did Marie's mother put some coins in the cake for? 

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小题3: How many coins did Marie's family find after eating the Cake?

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小题4:How long didn’t Marie speak?

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小题5:Could Marie speak at last?

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单项选择题