單項選擇題辦理允許推送作業(yè)后,車列未占用推送進路時,駝峰場可拉出YTA,關(guān)閉駝峰復(fù)示信號,到達場的推送進路經(jīng)()延時后解鎖

A.10s
B.20s
C.25s
D.30s


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