4. Let $I$ be the incenter of $\triangle A B C$, and $\odot O$ be the circumcircle of $\triangle A B C$. Then the point that must lie on $\odot O$ is the ( ) of $\triangle B I C$.
(A) orthocenter
(B) circumcenter
(C) the reflection of the incenter over $B C$
(D) the reflection of the centroid over $B C$
4. B.

Let $\odot O^{\prime}$ be the circumcircle of $\triangle B C I$. Then
$$
\begin{array}{l}
\angle B I C=90^{\circ}+\frac{1}{2} \angle A . \\
\text { Also } \angle B O^{\prime} C=360^{\circ}-2 \angle I=180^{\circ}-\angle A,
\end{array}
$$

Therefore, $A, B, C, O^{\prime}$ are concyclic.