I hear he is ill in hospital. You'd better go           see him at once.    [ ]

A. so                          

B. or    

C. and                          

D. but

X（γ）线全身照射，治疗平面实测剂量率一般是用小于（）较为安全。

A.<5cGy／min

B.<10cGy／min

C.<20cGy/min

D.<30cGy/min

E.<50cGy/min