1. Given sets
$$
\begin{array}{l}
S_{1}=\left\{(x, y) \mid \lg \left(1+x^{2}+y^{2}\right) \leqslant 1+\lg (x+y)\right\}, \\
S_{2}=\left\{(x, y) \mid \lg \left(2+x^{2}+y^{2}\right) \leqslant 2+\lg (x+y)\right\} .
\end{array}
$$

Then the ratio of the area of $S_{2}$ to the area of $S_{1}$ is ( ).
(A) 99
(B) 100
(C) 101
(D) 102
-1.D.
$S_{1}$ represents the interior of the circle $(x-5)^{2}+(y-5)^{2} \leqslant 49$, with an area of $49 \pi$;
$S_{2}$ represents the interior of the circle $(x-50)^{2}+(y-50)^{2} \leqslant 4998$, with an area of $4998 \pi$.
Therefore, the ratio of the area of $S_{2}$ to the area of $S_{1}$ is 102.