A point equidistant from the endpoints of a segment not necessarily is on the segment, then, options A and D are discarded (the midpoint of the segment is on the segment). The angle bisector divides an angle in two equal angles, and is not applied to a segment; then, option B is discard. The perpendicular bisector of a segment divide a segment in two equal parts, then, all of its points are equidistant from the endpoints of the divided segment.
