单项选择题
A.强度高、块度大B.强度高、块度小C.强度低、块度大D.强度低、块度小
A.500B.1000C.1500D.2000
A.560B.570C.580D.590
A.1×0.6L/minB.1×0.8L/minC.1×0.9L/minD.1×1.0L/min
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