某不纯的硝酸铵中氮的质量分数为36%，则此硝酸铵中混入杂质可能_爱下问搜题

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问题选择题

某不纯的硝酸铵中氮的质量分数为36%，则此硝酸铵中混入杂质可能是[ ]

A．NH₄HCO₃

B．(NH₄)₂SO₄

C．CO(NH₂)₂

D．NH₄Cl

答案

答案：C

选择题

No one makes Mr. Green _____ so much work. But you can always find him _____ very late. [ ]

A. to do; working

B. do; to work

C. to do; to work

D. do; working

填空题

由于变频器具有电子热保护功能，一般情况下可不接______。