Final answer:
The perpendicular bisectors of any two sides of the triangle need to be completed first to construct a circle that circumscribes a triangle.
Step-by-step explanation:
In order to construct a circle that circumscribes a triangle, the perpendicular bisectors of any two sides of the triangle need to be completed first.
A perpendicular bisector is a line that passes through the midpoints of a side of a triangle and is perpendicular to that side. When the perpendicular bisectors of any two sides of a triangle are drawn, they intersect at a single point, which is the center of the circumcircle. The radius of the circumcircle is then the distance from the center to any vertex of the triangle.
Therefore, option A is the correct answer.