单选题 当输入f(k)=ε(k)时,某LTI离散系统的零状态响应为yzs(k)=[2-(0.5)k+(-1.5)k]ε(k),则描述该系统的差分方程为( )

A. y(k)-y(k-1)+0.75y(k-2)=f(k)-0.5f(k-1)

B. y(k)+y(k-1)-0.75y(k-2)=2f(k)+0.5f(k-2)

C. y(k)-y(k-1)+0.75y(k-2)=2f(k)-0.5f(k-2)

D. y(k)+y(k-1)-0.75y(k-2)=f(k)+0.5f(k-1)