Find the odd item (2D vs 3D objects): Identify the option that is a plane figure, unlike the others which are solid figures.

Introduction / Context:
Another classic geometry categorization: distinguish between two-dimensional plane figures and three-dimensional solids. Understanding dimensionality is a fundamental skill and yields an unambiguous odd-one-out here.

Given Data / Assumptions:

• Cube: 3D solid with 6 equal square faces, 12 edges, 8 vertices.
• Cuboid: 3D solid (rectangular prism) with 6 rectangular faces.
• Sphere: 3D solid with all points on the surface equidistant from the center; no edges or vertices.
• Square: 2D plane figure with 4 equal sides and 4 right angles.

Concept / Approach:
Classify by dimensionality. Solids have volume and three dimensions (length, width, height), while plane figures have area and two dimensions (length, width). Only one option is purely 2D.

Step-by-Step Solution:

Verification / Alternative check:
Check physical properties: volume exists for solids (cube, cuboid, sphere). Square has area but no volume, reinforcing the distinction.

Why Other Options Are Wrong:
Cube, cuboid, and sphere all unambiguously possess volume and are three-dimensional geometric solids.

Common Pitfalls:
Do not be misled by face shapes (e.g., cube faces are squares); the item itself must be judged, not its faces.

Final Answer:
Square