单项选择题
The seven segment arrangement for numerical(数字的) display on consoles, test meters and other applications can be either（）
A.UJT or BJT B.BCD or OCD C.JFET or IGFET D.LED or LCD
单项选择题 Usually, emergency electricity supplies to on board（）
单项选择题 Before doing any work on a hydraulic system equipped with accumulators, you should（）
单项选择题 The ability of lubricating oils to resist viscosity changes during temperature changes is indicated by the（）
