[单选] The mechanical exhaust valve operation system is replaced by（）in an electronic controlled ME engine.
A . a system with a Hydraulic Power Supply (HPS) unit B . a system with roller guides for exhaust valves C . a system with an electronically controlled Alpha Lubricator D . a system directly powered by electric motor
空闲时间是指工作时间没有执行（）的那段时间。
330～500kV线路的后备保护应按什么原则装设？
A wave entering（）is likely to produce bores． shallow water。 deep water。 river。 tide。
补画E-14视图中所缺的第三视图。
（）is not a type of tide. SEMIDIURNAL。 DIURNAL。 MIXED。 OSCILLATING。
The mechanical exhaust valve operation system is replaced by（）in an electronic controlled ME engine.
