It can't be a kite because the opposite angles wouldn't be supplementary. It can't be a nonconvex figure because the opposite angles wouldn't be supplementary. The figure is an isosceles trapezoid. The noncongruent sides are parallel, the two congruent sides are the transversals. These segments form two pairs of consecutive, supplementary angles.
Opposite angles are also supplementary.
The figure is an isosceles trapezoid. Two sides are congruent and the two bases are parallel. When there are two parallel lines cut by a transversal you can have same side interior angles, which means they're supplementary. There are 360 degrees in a trapezoid, and in an isosceles trapezoid base angles are congruent. 180 degrees for each leg.