Which statements are true about polygons? check all that apply.

1. all sides and all angles in a polygon are congruent.

2. the sides of a polygon are segments that intersect exactly two other segments, one at each endpoint.

3. in a polygon, all segments with a common endpoint are collinear.

4. if all of the sides of a convex polygon are extended, none of them will contain any points that are inside the polygon.

5. the extension of at least one side or diagonal in a concave polygon will contain a point that is inside the polygon.