Rhombus
quadrilateral
a trapezoid
parallelogram or a rhombus * * * * * Incorrect. A parallelogram or rhombus have two pairs (ie 4) of parallel sides, and that is not the same as exactly two parallel sides. The correct answer is any polygon with with four or more sides of which only two are parallel. The only one of these with a specific name is a quadrilateral and the name is a trapezium.
A polygon (joke). I don't think there is a name for that, though.
There is no particular name. It need not be a regular polygon - for example, consider a stretched hexagon.
Paralellagram * * * * * No. A parallelogram (check spelling) has two PAIRS of parallel sides which is not the same as exactly two parallel sides. The correct answer is any polygon with with four or more sides of which only two are parallel. The only one of these with a specific name is a quadrilateral and the name is a trapezium.
There is no generic name. Any polygon with 4 or more sides can have 2 parallel sides. There are also non-polygonal shapes that can have parallel sides: for example, a circle that is stretched out into a cigar shape can have two parallel sides.
For a 4-sided polygon (a quadrilateral), the shape is a trapezoid (trapezium in the UK).*The question was copied in and omitted the "4 sided" restriction. There are innumerable irregular polygons that have a single pair of parallel sides, those that have 5 or more sides.
The name of a polygon with 15 sides is a pentadecagon
Strictly speaking you cannot have one parallel side - you must have one pair. Any irregular polygon with four or more sides can have a pair of parallel sides. Most have no specific names - the only one that does is a trapezium.
There is no formula for how many sides there are in a polygon; the name of the polygon shows how many sides it has.
A pentagon is the polygon with 5 sides.