Answer:
D: an irregular quadrilateral
Explanation:
def not a rhombus : A rhombus is a special case of a parallelogram. In a rhombus, opposite sides are parallel and the opposite angles are equal.
def not a pentagon, cause it's got only 4 sides.
def not a regular quadrilateral which must have 4 equal sides, and 4 equal angles, and its diagonals must bisect each other. Square is the only quadrilateral that satisfies all these conditions.
only D: An irregular quadrilateral is a quadrilateral with four sides that are not regular or the same.