问题
单项选择题
Upon arrival at the discharging port, the inert gas system is（）.
A.turned on
B.turning on
C.turn on
D.to turn on
答案
参考答案：A
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Upon arrival at the discharging port, the inert gas system is（）.
A.turned on
B.turning on
C.turn on
D.to turn on
参考答案：A