Which polygon or polygons are regular?
A. A polygon with three sides is shown. All three sides are marked as congruent. All three angles are marked as congruent.
B. A polygon with four sides is shown. All four sides are marked as congruent. Two pairs of opposite angles are marked as congruent.
C. A polygon with four sides is shown. All four sides are marked as congruent. All four angles are marked as right angles.
D. A polygon with five sides is shown. Three sides are marked as congruent and the other two sides are not labeled. Two right angles are marked and the other three angles are not labeled.
Option A is a regular polygon, as it meets the criteria for a regular polygon, i.e., all sides and angles are congruent.
Option B is a regular quadrilateral, also known as a square.
Option C is a regular quadrilateral, also known as a rectangle.
Option D is not a regular polygon, as it has sides and angles that are not congruent.