Classification – Odd one out (tool → object of action) Three pairs name a tool and the typical object it acts upon. One pair names two similar stationary items rather than a tool–target relation. Identify the odd pair.

Introduction / Context:
Tool–target relations are common: the first item is used to act on/with the second (shovel→mud, screwdriver→screw, hammer→nail). A distractor may pair two peer items without an action relation. Spotting the presence or absence of directed action is decisive.

Given Data / Assumptions:

• Shovel : Mud
• Screwdriver : Screw
• Hammer : Nail
• Pen : Pencil

Concept / Approach:
Ask: “Is the second noun the usual object the first acts on?” Three are yes. One is simply two writing instruments, not instrument→target.

Step-by-Step Solution:
Shovel moves/handles mud → tool→material.Screwdriver drives/removes a screw → tool→object.Hammer drives a nail → tool→object.Pen and pencil are co-category writing tools → not tool→target → odd one out.

Verification / Alternative check:
Swap order: “nail : hammer,” “screw : screwdriver,” “mud : shovel” remain meaningful as target→tool. “pencil : pen” gives peer→peer, not actional symmetry, confirming the mismatch.

Why Other Options Are Wrong:

• Shovel : Mud → action relation present.
• Screwdriver : Screw → action relation present.
• Hammer : Nail → action relation present.
• None of these → only one lacks the relation (Pen : Pencil).

Common Pitfalls:
Accepting “pen : pencil” due to domain similarity. Classification demands relation uniformity, not mere topical similarity.

Final Answer:
Pen : Pencil