Magnetic repulsion from like poles facing each other

Steps:

• Examine each arrangement's facing poles or bars.
• Like poles (S-S or N-N) repel; unlike poles (S-N) attract.
• Non-magnetic bars (copper) allow no magnetic interaction; magnetic bars (iron, demagnetized) conduct fields but don't create poles.
• Identify setup with direct like-pole contact causing repulsion.

Why D is correct:

• In S S N S, the arrangement places two south poles facing (S-S) and two others (N-S attract, but initial S-S repels per the like-poles-repel law.

Why the others are wrong:

• A: S-N with iron attracts as unlike poles; iron conducts field without repulsion.
• B: S-N with copper has no magnetic interaction, so no repulsion.
• C: S-S-N has initial S-S repulsion, but overall S-N attraction dominates the setup.

Final answer: D