Stella is constructing a regular hexagon.

Here's the reasoning:

• The problem mentions that there are five arc markings on the circle, which divides the circle into six equal parts.
• Adding the additional point would complete the sixth arc, implying that the circle is divided into six equal arcs.
• A regular hexagon can be inscribed in a circle by dividing the circumference into six equal parts, corresponding to the six vertices of the hexagon.

Thus, the correct answer is: A regular hexagon.

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Would you like more details or have any questions about the construction process?

Related questions:

1. How do you construct a regular hexagon using a compass and straightedge?
2. What is the relationship between the number of sides of a polygon and its inscribed circle?
3. How can you use a compass to find the center of a circle?
4. How do the side lengths of a regular polygon inscribed in a circle relate to the circle's radius?
5. How can you construct a regular pentagon using a compass and straightedge?

Tip: In a regular polygon, the central angle (angle at the circle's center) can be found by dividing 360° by the number of sides.