This question requires a diagram to show the position of point D. I found an attachment with the same question which I attached it along with this answer.
Answer:
If AC = BC, then point D is equidistant from points A and B because a point on a perpendicular bisector is equidistant from the endpoints of the segment it intersects
Step-by-step explanation:
A line CD is a perpendicular line to line ACB intersecting point C. To understand it easier, if ACB is a horizontal lines, D is a point directly on top of C.
Any point directly on C which perpendicular to line ACB will always the same to the endpoint of the segments.