Which of the following shapes has the greatest number of sides?

A decagon is a polygon that has ten sides. To determine why this shape has the greatest number of sides among the options provided, let's look at the definitions of the other shapes in the list.

A quadrilateral has four sides, which makes it a simple four-sided figure. A hexagon has six sides, which is greater than a quadrilateral but still fewer than the ten sides of a decagon. An octagon has eight sides, further increasing the count, yet it still does not reach the number of sides in a decagon.

Given this information, the decagon stands out as the shape with the highest number of sides in this selection, confirming that it is the correct answer.