1. A rectangle has parallel sides that are congruent with each other.
2. The adjacent sides are always 90 degrees or perpendicular with each other.
3. The diagonals are also congruent with each other.
From the given choices.
XY is congruent to WZ, it satisfies the note #1 above, therefore this is true
XZ is congruent to YW, it satisfies the note #3 above, therefore this is true
XY is perpendicular to YZ, it satisfies the note #2 above, therefore this is true
XZ is perpendicular to WY, the diagonals are always equal but not necessarily formed a 90 degrees angle, therefore this is NOT necessarily true.
The answer is Choice D.