Final answer:
If 's' refers to a cone, the perpendicular cross-section to the base is a circle; if 's' refers to a cube, it's a square.
Step-by-step explanation:
The question seems to relate to the concept of conic sections which form different shapes when a plane intersects a cone at various angles. For example, if the intersection is perpendicular to the base of the cone and the cone is a right circular cone, then the resulting shape is a circle. On the other hand, if we're thinking about a cubic shape and considering its cross-sections, they could be squares if the section is parallel to a face or rectangles if it's at an angle to the faces but still perpendicular to an edge.
Based on the context provided, if 's' is referring to a three-dimensional shape like a cone or cube, we might conclude that the cross-section shape perpendicular to its base could be either a square or a circle. This would depend on whether 's' is a cone, leading to a circular cross-section, or a cube, leading to a square cross-section.