7. Given that $H$ is the orthocenter of $\triangle A B C$, the circumradius of $\triangle A B C$ is $R$, and the circumradius of $\triangle B H C$ is $r$. Then the relationship between $R$ and $r$ is ( ).
(A) $R=r$
(B) $R>\dot{r}$.
(C) $R<r$; when $\triangle A B C$ is an obtuse triangle, $R<r$
7. A. (Hint: It is known that $\angle B H C=180^{\circ}-\angle A$, in $\triangle B A C$, $B C=2 R \sin A$, in $\triangle B H C$, $B C=$ $2 r \sin \left(180^{\circ}-\angle A\right)=2 r \sin A$, thus $R=r_{.}$)