JAMB Physics 1980 Question 40

The best material for the core of the primary and secondary coils of an induction coil is

1. A.copper, because it is a good conductor of electricity
2. B.steel, because it becomes magnetic and retains its magnetism for a long time
3. C.rubber, because it is a good insulator and the user is prevented from shock
4. D.soft iron, because it becomes magnetic but easily loses its magnetism
5. E.glass, because it is transparent.