All but one _____ here just now. [ ]
A. is
B. was
C. has been
D. were
答案：D
下列指标可以评价AIDS患者的细胞免疫功能的是（）
A.CD2／CD3细胞比值
B.CD3／CD4细胞比值
C.CD3／CD8细胞比值
D.CD4／CD8细胞比值
E.CD2／CD4细胞比值
进入洁净区的空气如何净化？
