公式I+G+X＞S+T+M说明（）。 总供给大于总需求。 总供给等于总需求。 注入量小于漏出量。 总需求大于总供给。 注入量大于漏出量。
脉冲整流器与相控整流器相比的优点是效率高，谐波含量低。
Before starting an engine by air, the engine must（） be turned by a turning gear for at least one minute。 be turned by a turning gear for at least two minutes。 be turned at least one complete turn。 be turned at least two complete tur。
CRH2型动车组设有地址插。
The oil pressure and flow from each bearings can be checked when（） the lubricating pumps are stopped and the access doors are opened。 the lubricating pumps are running and the access doors are opened。 the engine is running and the access doors are closed。 the engine is stopped and the access doors are closed。
学校放暑假时，准备组织学生到欧洲修学旅游，他们到下列地区将看到的地理现象是（）
