单项选择题
A.〈0.2ms/cmB.≥0.5ms/cmC.≥0.3ms/cmD.〈0.1ms/cm
A.1~2g/cm3B.3~5g/cm3C.0.1~0.8g/cm3D.1~8g/cm3
A.5000lxB.20000lxC.70000lxD.50000lx
A.2000lxB.10000lxC.20000lxD.30000lx
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