We ______the luggage for him. His brother did it for him.

A．didn’t need carry

B．needn’t have carried

C．didn’t need to carry

D．needn’t carry

如果要将不同浓度水平质控结果标记在同一张控制图上，应采用（）

A.Z-分数图

B.平均值-极差控制图

C.Levey-Jenning质控图

D.平均值-s控制图

E.Shewhart图