Answer:
(d) perpendicular bisectors
Explanation:
The circumcenter is the center of the circumcircle of the triangle. Each vertex of the triangle lies on that circle. The sides of the triangle are chords of the circle.
The perpendicular bisector of a chord is a line that intersects the center of the circle containing the chord. Hence, the perpendicular bisectors of the sides of a triangle will intersect the circumcenter.