Question

Which shape could be thought of as being created by stacking congruent polygons?

Answer 1

You would form a prism. 

Answer 2

A polygon is composed of three or more line segments ,and when you join these segments ,a closed geometrical shape should form.For example, Equilateral triangle, Square, Regular Pentagon, Regular Hexagon,....

There are many possibilities.

→If you join an Equilateral and three other equilateral triangles having same base length,you will obtain, Equilateral Pyramid.

→If you join Square and four equilateral triangles having same base length,you will obtain, Equilateral Square Pyramid.

→Similarly, if you join Regualr Pentagon and five equilateral triangles having same base length,you will obtain, Equilateral Regular pentagonal Pyramid

→Regular Hexagon+Six equilateral triangles=Equilateral Regular Hexagonal Pyramid

→If you join six congruent squares ,you will get the shape of Prism called Cube.

These are known that is defined shape in mathematics which i have written.You can create many more shapes by yourself.