-The problem wasn't difficult for him,was it ?    

-______. He should have been given a more difficult one.    [ ]

A. No,it was      

B. Yes,it was      

C. Yes,it wasn't    

D. No,it wasn't

随机抽样调查了某地100例健康女性的血红蛋白含量，算得其均数为117g/L，标准差为10g/L，则其95%医学参考值范围为（）

A.117±1.645×10

B.117±2.58×10

C.117±2.58×10÷10

D.117±1.96×10÷10

E.117±1.96×10