11 Given that $x_{1}$ is a root of the equation $x+\lg x=3$, and $x_{2}$ is a root of the equation $x+10^{x}=3$, then the value of $x_{1}+x_{2}$ is ( ).
(A) 3
(B) 6
(C) 2
(D) 1
11 Since $\lg x=3-x, 10^{x}=3-x$, let $y=3-x$, then $y_{1}=\lg x, y_{2}=$ $10^{x}$ are inverse functions of each other. Therefore, the intersection points $A$ and $B$ of $y_{1}=\lg x$ and $y_{2}=10^{x}$ with the line $y=3-x$ are symmetric about the line $y=x$. By solving the intersection of $y=x$ and $y=3-x$, we get the midpoint $C\left(\frac{3}{2}, \frac{3}{2}\right)$ of segment $A B$, thus $x_{1}+x_{2}=3$. Therefore, the correct answer is A.