单项选择题
A、夹矸 B、老顶 C、直接顶 D、伪顶
A.小于1.3m B.1.3~3.5m C.2.O~4.5m
A.1.3~4.0m B.1.3~3.5m C.2.0~3.5m
A.1.5~4.0m B.1.3~3.5m C.大于3.5m
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