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问题
单项选择题
使用DT-830型数字万用表时，环境的相对湿度小于（）。
A.20%
B.40%
C.60%
D.80%
答案
参考答案：D
判断题
分析元素含量范围为0.1%~1%时，原子发射光谱分析精密度近似于化学分析。
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选择题
Now the world's attention _____ the stocking markets, as they have great influence in the world's economy.
A. is fixing on
B. has fixed on
C. is being fixed on
D. had been fixed on
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