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【简答题】
相较于其他的光源,LED灯更“干净”所谓的“干净”不是指的灯表面以及内部的干净,而是这个灯是属于( )源的,不会产生太多的( ),不会吸引那些喜光喜热的昆虫。
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举一反三
【简答题】普通调幅信号的（）与调制信号的（）
【单选题】In drawing up the plan, they went to the library to _____ many books. [ ]
A.
bring up
B.
referr to
C.
look for
D.
try on
【简答题】A.packing up to go abroad． B.Brushing up on her English． C.Drawing up a plan for her English course． D.Applying for a visa to the United States．
【简答题】A．Packing up to go abroad. B．Brushing up on her English. C．Drawing up a plan for her English course. D．Applying for a visa to the United States.
【简答题】用低频信号去改变高频信号______的过程，称为调幅。普通调幅信号的特点是：已调信号的包络变化与______信号变化规律相同，内含______分量，______分量和______分量。
【单选题】普通调幅信号电流的频谱和LC并联谐振回路阻抗的幅频特性和相频特性如图所示，则产生的普通调幅信号为（ ）。【图片】
A.
u AM = R e I sm [1 + m a cos( W t - p / 4)]cos w c t
B.
u AM = R e I sm (1 + m a cos W t )cos w c t
C.
u AM = R e I sm [1 + 0.707 m a cos( W t - p / 4)]cos w c t
D.
u AM = R e I sm (1 + 0.707 m a cos W t )cos w c t
【简答题】You might just as well tell the manufacturer that male customers ________ not like the design of the furniture. A．must B．shall C．may D．need
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