AB表示（ ）
AB同时发生
B. A发生
C. B发生
D. A,B至少有一个发生
In the street, he could feel the happiness of Christmas.
A. Worked
B. Walking
C. To work
D. Having worked
the questions are,he is able to answer them.
A. The more difficult; the likely
B. The difficult more; the likely less
C. The much difficult; the more likely
D. The more difficult; the less likely
牵引双管供风车体时，需将两机车的总风缸管进行连接，并开放折角塞门，再将无火机车两风泵右侧的双风管调压阀止阀和调压阀旁通阀均打到与管路垂直方向，调压阀旁通阀——机车重联供风塞门（）kpa。
A. 600
B. 900
C. 700
D. 800
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