青贮饲料之所以被人们所重视，能够大量保存（）是其重要原因。
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卫生部制定《医疗机构临床实验室管理办法》根据哪些法律、法规？
向施工封锁区间开行路用列车时，列车进入封锁区间的行车凭证为（）。
A. 路票
B. 调度命令
C. 红色许可证
D. 出站信号机的进行信号
In conventional systems, the injection pressure（）, while it’s（）in common rail diesel engines.
A. fluctuates with the engine speed to some extent, independent of the engine speed
B. keeps constant at all engine speed, dependent on the engine speed to some extent
C. keeps constant at all engine speed, independent of the engine speed
D. is decided by the engine speed, constant at all engine speed
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