单项选择题
A.5t B.10t C.20t
A.0.5m~1mB.1m~1.5mC.1.5m~2m
A.0.1m~0.2m B.0.3m~0.5m C.0.5m~0.8m
A.≥2m/hB.≥3m/hC.≥5m/h
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