单项选择题

Which correlation property makes filtering white noise by autocorrelation possible?

A.When τ=0,the autocorrelation function has the maximum value
B.The autocorrelation function of a periodic signal is still a periodic signal of the same frequency, but it does not retain the phase information of the original signal
C.The autocorrelation function of the random noise signal will decay rapidly as τ  increases
D.Two periodic signals with different frequencies are not correlated to each other
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