Difficulty: Easy
Correct Answer: sphere
Explanation:
Introduction / Context:Geometry distinguishes 2-dimensional (plane) figures from 3-dimensional solids. Three options are planar shapes, while one is a solid. Discriminating dimensionality is the core reasoning task here.
Given Data / Assumptions:
Concept / Approach:Classify by dimensionality. Triangle, circle, and oval lie in a plane (2D). A sphere is a 3D object with volume. Therefore, the sphere does not belong with the planar shapes.
Step-by-Step Solution:
triangle → 2D polygon.circle → 2D locus equidistant from a point.oval → 2D rounded figure (e.g., ellipse-like).sphere → 3D surface; set of points equidistant from a center in space.Verification / Alternative check:
Only “sphere” has volume and can cast a 3D shadow with thickness; the others are flat figures.Why Other Options Are Wrong:
triangle / circle / oval: All are 2D figures; they share the same dimensional class.Common Pitfalls:
Confusing “oval” and “ellipse” terminology; either way, it remains 2D, unlike a sphere.Final Answer:sphere
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