重写句子:Alan passed the test. Alan had studied hard. Alan had understood the material.(complex sentence)
Alan passed the test because Alan had studied hard and understood the material.
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作业车运行时,机车信号机应注意哪些事项?
当机车信号由双黄灯、双黄灯闪、交流计数黄灯变为白灯时,控制作业车前方()m停车。
发动机曲柄连杆机构采用压力润滑和()相结合的润滑方式。
静电除尘器的是结构包括()和机械两部分。
接触网作业车发动机的启动操作的注意事项有哪些?