(John of the clue crew reporting)  Because the geometric shape here has all right angles, it's called a rectangle; when they're not right angles, it becomes this type of quadrilateral
If the diagonals of a parallelogram are congruent, then it's a rectangle (
neither ... Before looking at any of these proof methods in action, here's a useful 
little... [DOC] [TLE] Example 4 - ClassZone [PAR] The opening must be a rectangle.