A polygon refers to a flat or two-dimensional shape which is closed and has straight sides. A polygon doesn't curved sides.
From the options given, the true statements about polygons include:
• The sides of a polygon are segments that intersect exactly two other segments, one at each endpoint.
• If all of the sides of a convex polygon are extended, none of them will contain any points that are inside the polygon.
• The extension of at least one side or diagonal in a concave polygon will contain a point that is inside the polygon.
Therefore, the correct options are B, D and E.
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