非电量保护的重动继电器宜采用启动功率不小于（）、动作电压介于55--65%Ue、动作

They have had a long and bitter struggle _____their living conditions.

A．to improving

B．for improving

C．to improve

D．improve

乳牙早失的诊断依据不包括（）

A.乳牙提前脱落

B.后继恒牙牙根尚未发育

C.后继恒牙牙根仅形成不到1／2

D.恒牙胚已暴露

E.牙冠面有较厚的牙槽骨质覆盖

肺癌治疗方法的选择是

A．腺癌首选放疗
B．鳞癌首选放疗
C．小细胞肺癌首选手术
D．鳞癌首选化疗
E．小细胞未分化癌首选化疗和放疗

Which of the following statements regarding yield spreads is least accurate The:（）

A. option cost in percentage terms can be computed by subtracting the OAS from the zero-volatility spread.

B. nominal yield spread measures the difference between the YTM on a risky bond and the YTM on a Treasury bond of similar maturity.

C. zero-volatility spread is the constant spread that is added to each Treasury spot rate to equate the present value of a bond’s cash flows to the price of an otherwise identical option-free bond.

引起中心静脉压升高的原因有

A．左心功能不全
B．输液过多过快
C．静脉回流加速
D．卧位转为立位