2. Statement D is correct. Statement A is correct because both squares and parallelograms have four sides and a quadrilaterals has four sides. Statement B is correct because a square is a parallelogram. Since they both share the same properties that lines of the opposite sides are parallel, this statement is correct as well. Statement C is correct because a trapezoid has one pair of parallel lines. Since all 3 statements are correct, statement D is correct.
4. I do not agree with this statement as a parallelogram does not have to have for sides of equal lengths but a square has. Also, a parallelogram may may not have all angles to be 90 degrees but in a square, all the angles are right angles.