Answer:
D. " No, the line should be perpendicular to the triangular faces"
Step-by-step explanation:
I took the test before and got it correct but if you would like an explanation:
A perpendicular cross section is meant to be perpendicular to the base of a 3-dimensional figure. The bases of triangular prisms are the triangles at either ends, and the rectangles make up the remaining faces.
Marco drew the line perpendicular to the rectangle faces because it was lying on it's side, he presumed it to be the base. But he was incorrect, the line should be parallel to the faces, perpendicular to the base. Therefore, option D is correct.