20) What is the distance from the centre to any point on the circle?

21) What is the part of a circle with horizontal and vertical radii making 90 Degree to each other?

22) What is the term for a quadrilateral whose all four sides are equal and its four angles are right angles?

23) What is the term for a quadrilateral if opposite sides are equal and parallel and all four sides are right angles?

24) What is the quadrilateral if all the four sides are equal, but only opposite angles are equal?