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【单选题】
我国国家标准规定的三个电压等级为安全电压等级,下面哪个不是安全电压。( )。A.
12V
B.
24V
C.
36V
D.
220V
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参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【简答题】vt. change sth., such as a decision, judgment, or process so that it is opposite of what it was before彻底改变
【单选题】听力原文： In this century, the wealth and success of nations will depend like never before on the ability to produce and use knowledge. Universities have long been instrumental in generating knowledge and...
A.
the change of Americans' attitude toward Afghanistan
B.
the necessity for university students to better understand foreign culture
C.
the fact that Afghanistan is affecting Americans' life
D.
the urgency for university students to understand Afghanistan issue
【多选题】利用紫外可见分光光度法鉴别的方法是
A.
比较最大吸收波长下的百分吸收系数
B.
对比吸收光谱图
C.
比较固定波长下的吸光度或吸光度比值
D.
比较最大吸收波长、最小吸收波长
【简答题】何首乌云锦花纹(异型复合维管束)存在的部位是
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