Question

select all the figures that have a triangular cross - section when sliced parallel to their bases.

Explanation:

Step1: Analyze first figure

It is a triangular - based pyramid. When sliced parallel to its base, the cross - section is a triangle.

Step2: Analyze second figure

It is a triangular prism. When sliced parallel to its base (the triangular base), the cross - section is a triangle.

Step3: Analyze third figure

It is a pyramid with a non - triangular base. When sliced parallel to its base, the cross - section is similar to the non - triangular base, not a triangle.

Answer:

The first two figures.