Classification — resource/consumable for a device vs removed material: Choose the odd pair: Petrol : Car, Electricity : Television, Ink : Pen, Dust : Vacuum cleaner.

Introduction / Context:
In three options, the second item uses/consumes the first as a resource to function (fuel, power, working medium). In one option, the second removes the first; it is not a resource.

Given Data / Assumptions:

• Car consumes petrol.
• Television consumes electricity.
• Pen uses ink to write.
• Vacuum cleaner removes dust; dust is not a power/fuel/working medium.

Concept / Approach:
Check whether the left-hand item enables the operation of the right-hand device or is merely the target of removal/cleaning.

Step-by-Step Solution:
1) Petrol → energy source for a car.2) Electricity → energy source for a television.3) Ink → working medium for a pen.4) Dust → unwanted material; vacuum cleaner removes it rather than using it.

Verification / Alternative check:
Ask: if you remove the left-hand item, can the device still operate normally? Removing fuel/power/ink disables operation; “removing dust” is precisely what the vacuum cleaner does.

Why Other Options Are Wrong:
They present authentic device–resource relations.

Common Pitfalls:
Over-generalizing “uses” to “interacts with.” Only resources/consumables count here.

Final Answer:
Dust : Vacuum cleaner