A pentagonal prism is cut by a plane perpendicular to the base. What is the shape of the cross section that is formed?

Question

A. 

a pentagon with one pair of equal sides

B. 

a trapezoid with one pair of parallel sides

C. 

a rectangle

D. 

a triangle

E. 

a hexagon

Answer 1

C. Rectangle

The base of the pentagonal prism is a rectangle

Imagine the plane moves an infinitesimal distance above the base of the pentagonal prism.

The intersection of this plane with the prism will have the same shape, a rectangle, as the base but with a different width as you move further up from the base.