The rule that something on a surface has to be measured with three measurements applies to:

• A. It applies to every object
• B. It applies to items on a surface
• C. It applies only to fragile items
• D. It does not apply to any item

Answer: (B)

When something sits on a surface, you need three independent measurements to pin down its position and orientation in space on that plane: two measurements describe where it lies on the surface (along two perpendicular directions), and the third records how high it sits above the surface or its tilt. Using three measurements helps prevent ambiguity that can come from perspective or uneven surfaces, so the rule is tied to items on a surface. If the item isn’t on a surface, or the context changes, the same three-measurement approach might not apply in the same way.