3. Given that point $I$ is the incenter of acute $\triangle A B C$, $A_{1} 、 B_{1}$ 、 $C_{1}$ are the reflections of point $I$ over sides $B C 、 C A 、 A B$ respectively. If point $B$ lies on the circumcircle of $\triangle A_{1} B_{1} C_{1}$, then $\angle A B C$ equals ( ).
(A) $30^{\circ}$
(B) $45^{\circ}$
(C) $60^{\circ}$
(D) $90^{\circ}$
3.C.

Since $I A_{1}=I B_{1}=I C_{1}=2 r$ (where $r$ is the inradius of $\triangle A B C$), point $I$ is also the circumcenter of $\triangle A_{1} B_{1} C_{1}$. As shown in Figure 5, let the intersection of $I A_{1}$ and $B C$ be point $D$. Then $I B=I A_{1}=2 I D$, so $\angle I B D=30^{\circ}$. Similarly, $\angle I B A=30^{\circ}$. Therefore, $\angle A B C=60^{\circ}$.