11、如果函数y = f(x-1)的反函数是y = f ^-1(x-1)，则下列等式中正确的是(    )                    

A．f(x)＝f(x-1)                          B． f(x) - f(x-1) = 1

C．f(x) - f(x-1) = -1            D．f(x)＝- f(x-1)