Polygons are two-dimensional closed figures that are formed by straight lines. They are composed of line segments that are connected end to end to form a closed shape. Polygons can have any number of sides, but some common examples include circles, squares, triangles, and rectangles.

Polygons:
Polygons are a type of geometric shape that exist in two dimensions. They are composed of straight lines called sides, which are connected end to end to form a closed shape. The sides of a polygon do not cross each other.

Types of Polygons:
There are many types of polygons, but some common examples include triangles, quadrilaterals, pentagons, hexagons, and octagons.

- Triangles: Triangles are polygons with three sides. They can be classified based on the lengths of their sides or the measures of their angles. Examples of triangles include equilateral triangles, isosceles triangles, and scalene triangles.
- Quadrilaterals: Quadrilaterals are polygons with four sides. They can also be classified based on the lengths of their sides or the measures of their angles. Examples of quadrilaterals include squares, rectangles, parallelograms, and trapezoids.
- Pentagon: A pentagon is a polygon with five sides. It is named after the Greek word "penta," which means five.
- Hexagon: A hexagon is a polygon with six sides. It is named after the Greek word "hexa," which means six.
- Octagon: An octagon is a polygon with eight sides. It is named after the Latin word "octo," which means eight.

Understanding the Given Options:
a) Quadrilaterals: Quadrilaterals are a type of polygon that have four sides. While squares and rectangles are examples of quadrilaterals, this option does not encompass other shapes like triangles and circles.
b) Rectangular prisms: Rectangular prisms are three-dimensional shapes, not two-dimensional polygons. Therefore, this option is not correct.
c) Polygons: This option is correct because polygons are two-dimensional closed figures formed by straight lines, and the given shapes (circles, squares, triangles, and rectangles) are all examples of polygons.
d) Shapes: While the given shapes are indeed examples of shapes, this option is too broad and does not specifically refer to two-dimensional closed figures.

Therefore, the correct answer is option 'C' - polygons.

C is the right answer because these all are polygons.