What is the answer to this geometry question

One step in construction uses the endpoints of segment AB to create arcs with the same radii. The arcs intersect above and below the segment. What is the relationship of AB and the line connecting the points of intersection of these arcs?
1) collinear
2)congruent
3)parallel
4)perpendicular

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I crossed out collinear and parallel. I know parallel isn't it since they're not on-top of each other. Help? I'm doing this from my Geometry Practice Tests For Regents Examinations.

these point when join are the perpendicular to the original line.

so, answer is 4.