A plane cuts through a rectangular prism. The plane is parrallel to the base of the rectangular prism. What is the shape of cross section?

rectangular.

Since the plane is parallel to the base of the rectangular prism, the shape of the cross section will be the same as the shape of the base.

To determine the shape of the cross section created by a plane that cuts through a rectangular prism, you need to understand how the plane intersects the prism.

In this case, the plane is parallel to the base of the rectangular prism, which means it slices through the prism's height but does not affect the length or width of the base. Therefore, the cross-sectional shape will have the same dimensions as the base of the prism, which is a rectangle.

So, the shape of the cross section formed by a plane parallel to the base of a rectangular prism is also a rectangle.