Answer:
"Select" is rectangle, and the dimensions are 9 cm x 5 cm
Step-by-step explanation:
A cross section is the space in which the plane and 3-D object intersect. Since the plane is horizontal (or in other words, parallel) to do the base, the dimensions of the cross section will be the same as the dimensions of the base of the prism, which is 9 cm x 5 cm. It will also be the same shape of the base, which is a rectangle. I can't see the option to click "9 cm x 5 cm" in the picture, but if you scroll down, you'll probably find it.