电容分相式异步电动机的两个定子绕组在空间上相隔（）。 A.30° B.90° C.4

_______ a precious diamond necklace for his wife, Martin could hardly afford a tie for himself.

[      ]

A. Having bought

B. Buying

C. Being bought

D. To buy

医学伦理学最突出的特征是（）。

A.实践性、继承性

B.时代性、人道性

C.人道性、全人类性

D.全人类性、继承性

E.人道性、实践性

一远视患者，裸眼远视力0.6，主觉验光用+2.5D镜片后，远视力提高到1.2。再增加镜片度数不再提高。对此患者而言+2.50DS是其（）。

A.绝对远视

B.可矫正远视

C.显性远视

D.隐性远视

E.总合远视

20. His parents were teachers in that school, _______ lost their lives in order to save

their students in the earthquake. 

A．none of them

B．both of them

C．none of whom

D．both of whom

气动分度盘由一个气控或电控二位三通阀输出脉冲信号来实现（）运动。