A circle is one possible answer.
It is a trapezoid that has one set of opposite parallel lines of different lengths.
trapezoid
A parallelogram always has one set of parallel lines, plus another set also.A trapezoid (trapezium) always has exactly one set of parallel lines and no more.Any shape with more than four sides can have one set of parallel lines, but doesn'tnecessarily have to.
A trapezoid has 1 set of parallel lines
a trapezuim
Trapezium.
an octagon it has eight sides
a rectangle is a shape that has two sets of parallel lines a trapezoid only has to have one set of parallel lines
hexagon
trapezoid
Trapezium (Uk English)
There are many, the simplest that I can think of is an isosceles trapezoid.