To choose which of the given quadrilaterals is not a parallelogram, let's recall all Conditions of Parallelograms. Let's start with the first condition.
If both pairs of opposite sides
of a quadrilateral are congruent,
then the quadrilateral is a parallelogram.
According to this condition, the quadrilateral from answer B is a parallelogram. Let's move to the next condition.
If both pairs of opposite angles of
a quadrilateral are congruent,
then the quadrilateral is a parallelogram.
In our exercise we do not have any quadrilateral with both pairs of opposite angles congruent. Therefore, let's move to the third condition.
If the diagonals of a quadrilateral
bisect each other,
then the quadrilateral is a parallelogram.
Using this condition, we can state that the quadrilateral from answer C is a parallelogram. Finally,it is time for recalling the last condition.
If one pair of opposite sides of a quadrilateral
is both parallel and congruent,
then the quadrilateral is a parallelogram
According to this condition, the quadrilateral in answer A is also a parallelogram. Therefore, only the quadrilateral in answer D does not match any of the above conditions.
