by Serhiy Grabarchuk Jr
To complete the overall sequence the shape intended to replace the question mark should consist of certain elements. What are they?
Each shape in the row contains a certain number of right angles within its outline: 1, 2, 3, …, and 5. The missing shape in this sequence should embrace 4 right angles. This is either a rectangle or a square. Since all other shapes can be inscribed into a square the missing shape is the square consisting of 4 segments.