( )are devices that are used to detect, and often to measure, the magnitude of something.
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Photoelectric sensors are composed of two basic components: a transmitter (light source) and a ( ).
An( ), in the electrical sense, is any device that convents an electrical signal into mechanical movement.
【单选题】【难度:1】ERP系统起源于( )的信息计划与管理,其形成发展大致经过5个阶段。
A. 制造业
B. 零售业
C. 建筑业
D. 金融业
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