1. Diamagnetic Materials (A): These materials are weakly repelled by magnetic fields. Copper (II) is a classic example of a diamagnetic substance (along with water, bismuth, etc.).
2. Paramagnetic Materials (B): These materials are weakly attracted by magnetic fields. Aluminium (III) is a standard example of a paramagnetic substance (along with sodium, calcium, etc.).
3. Hard Ferromagnets (D): These materials have high coercivity and retentivity, making them suitable for permanent magnets. Alnico (I) (an alloy of Aluminium, Nickel, and Cobalt) is a well-known hard ferromagnetic material.
4. Soft Ferromagnets (C): These materials have low coercivity and are easily demagnetized. By elimination in this specific list, Gadolinium (IV) is matched here (Gadolinium is a ferromagnetic lanthanoid with a Curie temperature near room temperature).

Conclusion: The correct matching is A-II, B-III, C-IV, D-I.