You_____ all those calculations! We have a computer to do that sort of thing.

A．needn’t have done

B．must not have done

C．shouldn’t have done

D．can not have done

非水滴定法测定维生素B₁原料药的含量，应选

A．淀粉指示剂
B．喹哪啶红-亚甲蓝混合指示剂
C．二苯胺指示剂
D．邻二氮菲指示剂
E．酚酞指示剂