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?

25) What is the quadrilateral if the two sides are parallel and all the four angles are different and the diagonals do not bisect at right angles?