测定以下（）时，水样不需要避光保存A、Cl- B、F- C、I- D、SO42?_爱下问搜题

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问题单项选择题

测定以下（）时，水样不需要避光保存

A、Cl-

B、F-

C、I-

D、SO42?

答案

参考答案：C

选择题

.After the new technique was introduced, the factory produced _____ cars in 2002 as the year before.

A．as many twice

B．as twice many

C．twice many as

D．twice as many

单项选择题

某DNA分子含腺嘌呤520个，占碱基总数的20%，该DNA分子中含胞嘧啶（）

A.350

B.420

C.520

D.780