A convex quadrilateral may have a reflex angle.

The point $Q$ and $U$ lie in the interior of the quadrilateral.

The points $R$ and $T$ do not lie on the quadrilateral.

The point $P$ lies on the quadrilateral.

The point $S$ lies in exterior of the quadrilateral.

Each pair of the opposite sides of a parallelogram is parallel.

The opposite sides of a parallelogram may not be equal.

The opposite angles of a parallelogram are equal. 

The diagonals of a parallelogram are equal.