Fred’s grandfather _______three years ago. He _______for three years.

A．died; died

B．was dead; died

C．died; has been dead

D．died; has died

关于CR摄片特点的说法，下列哪项是错误的（）

A.感光度高，照射量可大幅度减低

B.具有广泛的动态范围

C.空间分辨率高

D.可进行减影

E.数字图像