Step 1: Understanding the category.
Among the given items, three are writing instruments — pen, marker, and pencil — while one is an object used for writing on, not for writing with.
Step 2: Analyzing the options.
- (a) Pen: Used for writing.
- (b) Marker: Used for writing or marking.
- (c) Paper: The surface to write on — not a writing tool.
- (d) Pencil: Used for writing or drawing.
Step 3: Conclusion.
“Paper” is the odd one out because it is not a writing instrument but a writing medium.