Question

a right rectangular pyramid is sliced vertically (down) at the red line by a plane not passing through the vertex of the pyramid. what is the shape of the cross - section?
a. trapezoid
b. triangle
c. cylinder
d. rectangle

Explanation:

When a right rectangular pyramid is sliced vertically by a plane not passing through the vertex, the cross - section has one pair of parallel sides (from the base and the opposite side of the slice) and two non - parallel sides. This matches the definition of a trapezoid. A triangle would require the plane to pass through the vertex. A cylinder is a 3D shape, not a cross - section here. A rectangle would need specific parallel and perpendicular side conditions which are not met as the sides from the non - base part of the pyramid are slanting.

Answer:

A. Trapezoid