对于强贯穿辐射，国际辐射防护委员会建议个人剂量当量中测算深度为（）
A.5.0mm
B.8.0mm
C.10mm
D.20mm
E.25mm
参考答案：C
3a2表示的是3×a×a。[ ]
My sister often with her friend Anna.[ ]
A. plays
B. play
C. playing
D. to play
