【简答题】某放大电路的通频带是40Hz~40kHz,如果输入信号为(a)u i =10sin(2π×60×10 3 t)mV;(b)u i =10sin(2π×15×103t)+2sin(2π×30×10 3 t)mV;(c)u i =10sin(2π×15×10 3 f)+2sin(2π×60×10 3 f)mV,试问输出波形是否会出现频率失真?
【单选题】Why one may have many good friends, but only have one the best/close friend?( )
A.
Because best friend can be satisfied with your any need.
B.
Because the best friend can help and support you whatever you do .
C.
Because the best friend is people’s only treasure.
D.
Because people may choose different good friends for different activities ,but a close friend is a person who you can rely on when you need help and who is able to share joys and sorrows with you.