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问题 单项选择题

数据库系统的核心是

A．编译系统

B．数据库

C．操作系统

D．数据库管理系统

答案

参考答案：D

解析：解析：数据库系统有数据库、数据库管理系统和用户组成。其核心是数据库管理系统。

阅读理解

Mark is a waiter. He doesn’t like his job. He has to work in the evenings. He sometimes has to work on weekends. He is always busy. Sometimes he has no time to eat dinner. His job is hard, and it isn’t fun. Mark likes to work, and he likes to meet people. But he doesn’t want to work in a restaurant. He wants to work in a bank. He wants to be a bank clerk.

Lisa is a nurse. She wears a white uniform. She works in a hospital. She helps doctors. She sometimes works at night. Usually she works in the day, and she gets up at six o’clock every morning. Lisa’s job is difficult and busy, but she doesn’t want to do anything else. She loves it.

根据短文内容，判断正（T）误（F）。

小题1:Mark likes to work in a restaurant.

小题2:Mark wants to be a bank clerk.

小题3:Mark doesn’t need to work on weekends.

小题4:Lisa sometimes works late.

小题5:Lisa wants a different kind of job.
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单项选择题

由外来杂质诱导成核过程称（）

A.初级成核

B.次级成核

C.均相成核

D.非均相成核
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