The correct answer is:
Connect two arcs together with a compass.
Step-by-step explanation:
When inscribing polygons, most polygons require two arcs to be connected at some point.
For a dodecahedron, we at one point must bisect an angle, which requires connecting two arcs.
For a square, you either bisect angles or draw a perpendicular bisector; both require connecting two arcs.
For an octagon, you bisect quadrants, which requires connecting two arcs.
Doubling the number of sides of an inscribed polygon is done by bisecting the segments of the circle; again, this requires connecting two arcs.