国开题库
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Please don’t make so much noise. The baby ________ now.
#A. slept#B. issleeping#C. sleeps
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Please ___________ an open return flight from Barcelona to Frankfurt.
#A. paper#B. text#C. book
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PLC在工作时采用（ ）原理循环扫描。
#A. 巡回扫描原理#B. 输入输出原理#C. 集中采样#D. 分段输出原理
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PLC是指？
#A. 个人电脑#B. 可编程控制器#C. 数控技术#D. 触摸屏
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PLC工作过程中，( )是按照顺序将所有信号读人到寄存输入状态的输入映像区中存储。
#A. 输入采样阶段#B. 程序执行阶段#C. 网络通信#D. 输出刷新阶段
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PLC的工作方式是
#A. 等待工作方式#B. 中断工作方式#C. 扫描工作方式#D. 循环扫描工作方式
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NPN型三极管的微变等效电路是
#A. #B. #C. #D.
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Nowhere else in the world _________ more attractive scenery than in Switzerland.
#A. you can find#B. has been found#C. can you find
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Normally, the price ____________ be marked on the shelf.
#A. issupposedto#B. isunlikelyto#C. issimilarto
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No more having to buy expensive textbooks which you will only use for a year or two and then sell or _______ away.
#A. get#B. give#C. take
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