Which of the following is the best definition of a perpendicular bisector?
A. A perpendicular bisector intersects a segment at its midpoint.
B. A perpendicular bisector intersects a segment at a 90-degree angle.
C. A perpendicular bisector divides an angle into two congruent angles.
D. A perpendicular bisector intersects a segment at its midpoint and at a 90-degree angle.