单项选择题
A.0.6~0.8m B.0.8~1m C.1~1.5m D.视巷道高度而定
A.0.15 B.0.3 C.0.6 D.0.9
A.30 B.40 C.50 D.60
A.0.1 B.0.2 C.0.3 D.0.4
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