Question

Taken parallel to the base, which of the following solids has a cross section that is not a rectangle? A. rectangular pyramid B. square pyramid C. triangular pyramid D. rectangular prism

Answer 1

C.  This is because if you cut it in a plane parallel to the ground, the triangular pyramid (tetrahedron) you get a triangle, not a rectangle.  (Note that the square is a special case of a rectangle and is therefore considered to be one)