单项选择题
如图所示波形可表示为()。
A. f(t)= ε (t)+ ε (t-1)+ ε (t-2)- ε (t-3) B. f(t)= ε (t)+ ε (t+1)+ ε (t+2)-3 ε (t) C. f(t)= ε (t)+ ε (t-1)+ ε (t-2)-3 ε (t-3) D. f(t)=2 ε (t+1)+ ε (t-1)- ε (t-2)
A.A B.B C.C D.D