Which statements are true about polygons? Choose three correct answers.

A concave polygon has an inward “dent,” so the extension of at least one side or diagonal can pass through the polygon’s interior. In a polygon, each side meets exactly two other sides, one at each endpoint, making C true. For a convex polygon, the line extending any side stays on the boundary or outside the interior, so D is true. B describes a regular polygon, not every polygon, and sides meeting at a common endpoint are not necessarily collinear.

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