Question

You are working on a proof. You know that A and B are on the perpendicular bisector of CD. What can you conclude?

Answer 1

A point on the perpendicular bisector of a  line segment
is equidistant from the ends of the segment.

So
           AC = AD
and
           BC = BD .

This can sometimes be very useful.

Answer 2

On USA test prep the answer should be C