The shape is polygon if it closed by by finite number of side.
So circle is not a polygon.
The polygon is convex if all the interior angle of polygon is less than 180 degree and polygon is concave if any one angle is greater than 180 degree.
The second shape is closed by finite number of side and all the interior angles are less tha 180 degree so it is conved polygon.
The third shape is also closed by finite number of side but two of interior angle is more than 180 degree so shape 3 is concave polygon.
Answers:
Shape 1: Not a polygon.
Shape 2: Convex polygon
Shape 3" Concave polygon.