Option D is correct.
A square and a parallelogram are quadrilaterals as they are both 4-sided.
Opposite sides of a square and a parallelogram are parallel:
The quadrilateral is a trapezium. A trapezium has one pair of opposite sides equal in length, which is the pair of lines that are not parallel to each other, and the other pair not equal in length, which is the pair of lines that are parallel to each other. It also has a pair of opposite angles that are supplementary.
No, I do not agree with the statement. The lines of a parallelogram are not of equal length, only the opposing lines are of the same length, while for the square, all lines are of equal length. Therefore I do not agree that all parallelograms are of equal length.