In modern times, the development of science is  ________ .

A．thought well of

B．thought highly

C．highly thought of

D．well thinking of

已知某单能射线在钢中的半价层为3mm，则该射线在钢中的吸收系数为（）。

A.0.231cm

B.2.31cm^－1

C.2.079cm

D.0.00231mm^－1