1. The range of the function $y=f(x)$ defined on $\mathbf{R}$ is $[m, n]$. Then the range of $y=f(x-1)$ is $(\quad)$.
(A) $[m, n]$
(B) $[m-1, n-1]$
(C) $[f(m-1), f(n-1)]$
(D) Cannot be determined
1. A.

When the graph of a function is shifted left or right, the range of the function does not change.