Answer: Copper isn't ferromagnetic,
Aluminum isn't ferromagnetic,
String has a ferromagnetic property
Explanation: first of all it is important to understand that all materials have diamagnetic effect.
From this we can explain two distinct property which is Paramagnetism and Ferromagnetism.
1.What do we understand by a paramagnetic material?
Ans- this describes a material that doesn't retain it's magnetic property even when the magnetic field has been removed, an example is Aluminum.
2. Ferromagnetic materials describes those type of materials that even after the removal of magnetic field retains it's magnetism. A good example of this is Iron, nickel etc.
By definition ferromagnetism is a basic property ( which depends on temperature, crystal Structure, chemical composition, etc.) That gives a material that attraction to magnet's and can form permanent magnet.
So from the examples listed in the question,
1. copper doesn't follow as a ferromagnetic material because it requires so much magnetic field to operate and is so weakly magnetized.
2. We already established aluminium as a paramagnetic material because of its weak ability to retain magnetism in the absence of magnetic field.
3. String because of its component which is (iron+carbon) has the ability to form ferrous metals.
