Aplane intersects this rectangular prism perpendicular to the prism’s base.

which two-dimensional figure is the cross section that results from the intersection of the plane and the prism?

Rectangle

try it with a briefcase and put a cardboard in it (of cours you don't have a brief case, it has gone mostly extinct)

ok, try it with a laptop
close the laptop
how can you read what I'm typing when you close your laptop
close the laptop
slide a paper into the middle of the opening
open laptop
surprise, it is a rectangle

rectangle