To identify the set with the stronger interaction between the charged objects, the most relevant question the student can ask is: Are the objects both positively charged or both negatively charged?
This question is crucial because the interaction between two charged objects depends on the type of charges they carry. Like charges repel each other, while opposite charges attract. The nature of the charges will determine the strength and type of interaction experienced by the objects.
The other questions about distance, mass, or size may have some influence on the interaction strength, but determining whether the charges are like or opposite will provide the most direct insight into the nature of their interaction.