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搜题
【单选题】
PWM调制器产生的调宽脉冲的特点是（）。A.
频率变化，脉冲的“占空比”正比于控
B.
频率变化，脉宽由频率发生器产生的脉冲本身决定
C.
频率不变，脉宽也不变
D.
频率变化，脉宽随控制信号Usr变化而变化
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反馈参考答案：
举一反三
【单选题】When was the Message Group founded?
A.
Several days ago.
B.
Several weeks ago.
C.
Several months ago.
D.
Several years ago.
【简答题】at a terrific rate
【判断题】In Oxford and Cambridge the BA converts to an MA several years later, upon payment of a fee.
A.
正确
B.
错误
【简答题】In a single moment, a good reader picks up ________. A) several words B) several phrases C) several sentences D) several lines
【判断题】In Oxford and Cambridge the BA converts to an MA several years later, upon payment of a fee.
A.
正确
B.
错误
【单选题】垂体功能减低性矮身材
A.
HA=BA＜CA（CA：时间年龄 BA：骨龄 HA：身高年龄）
B.
HA＜BA=CA
C.
BA＜HA＜CA
D.
BA＞HA＞CA
E.
HA=BA=CA
【简答题】B A powerful earthquake measuring 7.0 on the Richter scale shook Haiti on Tuesday, causing several buildings to collapse in the Western hemisphere's poorest nation and leading to an unknown number of ...
【单选题】IMPORTANT: MOMENTOUS::
A.
terrific : affectionate
B.
supple : mellifluous
C.
commodious : solicitous
D.
relevant : crucial
E.
desperate : deprived
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