用作液体制剂的防腐剂是（）A.羟苯酯类 B.阿拉伯胶 C.阿司帕坦_爱下问搜题

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问题单项选择题

用作液体制剂的防腐剂是（）

A.羟苯酯类

B.阿拉伯胶

C.阿司帕坦

D.胡萝卜素

E.氯化钠

答案

参考答案：A

单项选择题

算术平均值中误差为观测值中误差的多少倍（）？

A.n

B.1／n

C.

D.1／

选择题

After ________ seemed a hopeless wait, four coalminers trapped in the mine for 125 hours were finally rescued in Heilongjiang Province.

A．when

B．that

C．it

D．what