Final answer:
Magnets with opposite poles would be most strongly attached due to the attractive force between unlike magnetic poles, which is stronger than any other listed combination.
Step-by-step explanation:
The objects that would be most strongly attached to each other are magnets with opposite poles. This is because unlike poles of magnets attract each other, which means a north pole and a south pole will be drawn towards each other, creating a strong attachment. This principle of magnetism is what makes magnetic attraction a powerful force. The magnetic field lines become denser between opposite poles, leading to a strong attractive force that is much stronger than any of the other combinations listed, such as oil and water, sand and air, or wood and metal, none of which exhibit magnetic properties in a way that would lead to a strong attraction.