Answer
Check Explanation for know-how and the images of the required cross-sections.
Step-by-step explanation
To draw these cross-sections, it'll be better to first sketch a rectangular prism to make it all clear.
We can see that a rectangular prism is essentially a cuboid.
And we also know that cross sections are intersections of a plane we put across the figure and the three dimensional figure.
For vertical cross section, the plane will cut vertically throught the rectangular prism and what we have at the end of the day is a vertical rectangle that is parallel to one of the side faces of the prism.
Vertical cross section
For the horizontal cross section, the plane cuts horizontally through the middle of the rectangular prism and the result is a rectangule that is parallel to the base of the rectangular prism.
But, we can rotate this to show how truly rectangular it is just like below,
Hope this Helps!!!