使用JSS-4A型晶体三极管测试仪时，接通电源预热5分钟后才可以使用。
参考答案：对
数据库结构的描述和定义是DBMS运行的基本依据，它们存储于
A．封锁表
B．数据字典
C．索引
D．日志
根据下面提供的情景，写一段接续文字。词数不少于50。
You have been given a chance to design a class meeting. You can choose whatever topic to make the meeting meaningful and instructive. What might be your topic? Why would you choose this topic? Give two or more reasons to explain.
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