Answer:
B. A circle circumscribed about a triangle
Step-by-step explanation:
The circumcenter of a triangle is where the perpendicular bisectors of the sides meet. The center of a circle is always on the line that is the perpendicular bisector of any chord. The sides of a triangle are chords of the circumcircle.
The given step would allow you to identify the center of the circumcircle, hence construct that circle.
