脊髓灰质炎病毒主要侵犯（）
A.前角运动神经元
B.交感神经节
C.白质纤维
D.后角感觉神经元
E.室管膜细胞
参考答案：A
Peter has many friends;_________can help him.
A．few of which
B．few of whom
C．few of that
D．few of them
压缩机和热力膨胀阀将蒸汽压缩式制冷系统分隔为“高压侧区”和“低压侧区”。
