单项选择题
A.0.5 B.1.0 C.1.5 D.2.0
A.20m2,4mB.20m2,4.5mC.30m2,4mD.30m2,4.5m
A.年有效剂量≤2.5mSv B.周围剂量当量率≤2.5μSv/h C.年有效剂量≤0.25mSv D.周围剂量当量率≤0.25μSv/h