Classification – Stationery vs writing surface: pick the odd one out. Three are writing instruments; one is the medium/surface written upon. Which option does not belong? Options: Pen, Marker, Paper, Pencil.

Introduction / Context:
In everyday items, the tool vs medium distinction is a common classification rule. Pens, markers, and pencils are instruments; paper is the medium upon which they act.

Given Data / Assumptions:

• Pen: writing instrument.
• Marker: writing/marking instrument.
• Pencil: writing instrument.
• Paper: writing surface/medium.

Concept / Approach:
Group by role in the writing process: instrument vs substrate.

Step-by-Step Solution:
Step 1: Identify instrument vs surface.Step 2: Pen/Marker/Pencil are instruments.Step 3: Paper is the surface; therefore, it is the odd one out.

Verification / Alternative check:
Usage context confirms the operational split: tools act on the medium.

Why Other Options Are Wrong:
Pen/Marker/Pencil: All are tools and fit the majority group.

Common Pitfalls:
Ignore brand/type variations; the function is the key criterion.

Final Answer:
Paper