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【单选题】
以下关于发声和发声体的说法中错误的是（ ）A.
声音在15℃的空气中的传播速度是340m/s
B.
声音在真空中的传播速度最大
C.
被敲响的音叉停止振动后，不再发声
D.
声音在固体和液体中传播速度比空气中传得快
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皮皮学刷刷变学霸
举一反三
【单选题】由集成运放A1、A2等元器件组成的反馈放大电路如图所示。设A1、A2均为理想运放。电阻R 2 阻值增加,则级间负反馈的反馈深度将________;
A.
增大,
B.
减小,
C.
不变
【简答题】本课程有多少学时?
【单选题】You are having a business lunch when your phone rings. It is an important phone call that you have been waiting for days. So the polite way to handle this situation is _______.
A.
take the call at the table and try to be quiet so you won’t disturb the other diners during the call
B.
turn your phone off completely and collect your voice mail messages afterward
C.
tell your associates at lunch that you’re expecting an important call, put your phone on vibrate mode and when the call does come, excuse yourself, leave the table and go to a place where no one can hear you. When you return to the table, thank your guest allowing you to take the call and don’t apologize or talk about the nature of the call.
【判断题】我们要充分认识和准确把握香港、澳门在新时代国家改革开放中的定位,支持香港、澳门抓住机遇、乘势而上,培育新优势,发挥新作用,实现新发展,作出新贡献。
A.
正确
B.
错误
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