诊断PNH，可用流式细胞术分析红细胞和白细胞膜的（）和（）表达。
参考答案：CD55；CD59
引起脑萎缩的最常见原因是（）
A.脑水肿
B.脑外伤
C.脑动脉粥样硬化
D.脑脓肿
E.肺部感染
Three fourths of the homework _______ today.
A．has finished
B．has been finished
C．have finished
D．have been finished
