There is no opposite for a quadrangle, a typically square area or courtyard between buildings, as at a school.
Any quadrangle with two opposite angles which are 90 degrees.
Rhombus!
square
square
Yes - since the definition of a parallelogram is "...a quadrangle with opposite sides and angles equal..."
rhombus
Such a figure is called a trapezium (UK) or trapezoid (US).
Any parallelogram, including rhombus, but not including rectangle or square.
A trapezoid is a quadrangle.
No, but a parallelogram is a quadrangle.
No, but a parallelogram is a quadrangle.
Yes, a trapezoid is a quadrangle because a quadrangle has four sides and a trapezoid has four sides.