5. The graph of the function $y=f(x)$ is $C$, and the graph symmetric to $C$ with respect to the line $x=1$ is $C_{1}$. After shifting $C_{1}$ to the left by 1 unit, the resulting graph is $C_{2}$. Then the function corresponding to $C_{2}$ is ( ).
(A) $y=f(-x)$
(B) $y=f(1-x)$
(C) $y=f(2-x)$
(D) $y=f(3-x)$
5. B.
$$
\begin{array}{l}
C_{1}: y=f(2-x), \\
C_{2}: y=f(2-(x+1))=f(1-x) .
\end{array}
$$