Question

identify the cross section of the tetrahedron.
assume objects are perpendicular if they appear so.

Explanation:

A tetrahedron is a triangular pyramid. The green plane cuts through 4 edges of the tetrahedron, creating a four-sided figure with one pair of parallel sides (the cross-section is a trapezoid, as the plane is oriented such that it is parallel to one edge and cuts through the other three faces, resulting in two parallel sides of different lengths).

Answer:

C. The trapezoid (the third blue shape from the left)