If an isosceles triangle ABC is inscribed in a circle of radius 'r'cm.Then its circumcenter is

Question

$\begin{array}{1 1}(A)\;\large\frac{r}{3}\normalsize\text{ cm away from A}\\(B)\;\large\frac{r}{2}\normalsize\text{ cm away from BC}\\(C)\;\text{2r cm away from C}\\(D)\;\text{Insufficient data}\end{array} $