The correct response that shows the first step in the construction of a perpendicular bisector is:
Image with alt text: A line segment has 2 end points, A and B. Two arcs, one open to the left and one to the right, are bisected by the line segment A B to the right of its center and left of its center, respectively.
This image depicts the process of drawing two arcs with the compass from points A and B, which is the first step in constructing a perpendicular bisector.