After Marco Polo came to China, he became friends with ________ Chinese emperor of _________ Yuan Dynasty named Kublai Khan.

A．an; the

B．a; the

C．the; a

D．a; a

假定血糖在常规实验室20天测定的质控结果的均数为6.5mmol/L，标准差为0.5mmol/L，在绘制单值质控图时，其控制图的控制线是（）

A.5.0～6.0mmol/L

B.4.5～6.5mmol/L

C.4.0～7.0mmol/L

D.3.5～7.5mmol/L

E.5.0～8.0mmol/L