单项选择题
当列车驾驶员听到所在调度区的调度员发起呼叫时,应在()内摘下话筒应答通话,否则列车驾驶员需重新发起呼叫请求。
A.10s
B.20s
C.0s
D.40s
E.60s
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单项选择题
A.10s
B.20s
C.0s
D.40s
E.60s
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