ABCD is a quadrilateral whose diagonal AC divides it into two parts, equal in area. Then, ABCD
Quadrilateral is any closed figure which has four sides.
Rhombus, Rectangle, Parallelograms are few Quadrilaterals.
When a Diagonal AC of a quadrilateral divides it into two parts of equal areas, it is not necessary for the figure to be a Rhombus or a Rectangle or a Parallelogram, it can be any Quadrilateral.