Can a trapezium contain two right angles?

YES!!! It is an Assymmetric Trapezium.

The Word 'Assymetric' means that it is not symmteric; that is one side is NOT a mirror image of the other.

So a pair of parallel lines, each of different length. On the left side ,say, you can have a vertical/right angled/90 degree intercepting line. On the right side , say, you can have an angled/sloping line. The two internal angles are one acute and the other obtuse, but their sum is 180 degrees. This is an assymetric trapezium.

A symetric trapezium the one sloping side is a mirror image of the other sloping side.