2
A trapezoid has one pair of parallel sides.
A trapezoid may have zero or one pair of congruent sides.
2 pairs
Zero
1
One pair.
A parellelogram has equal sides, the trapezoid is a parallelogram.
It doesn't need any in order to be a trapezoid. It can have a max of two pairs of perpendicular sides.
One pair
One pair.
It may have none. A trapezium (US) has no parallel sides. A trapezoid (US, known elsewhere as a trapezium) has one side of parallel sides.
2 sides