Answer:
D. It must be able to be magnetized.
Step-by-step explanation:
An electromagnet is a device formed by an iron core surrounded by a solenoid (coil). When an electric current passes through the coils of the coil, a magnetic field is created, which causes the elementary magnets of the iron core to orientate themselves, thus being magnetized and, consequently, with the property of attracting other ferromagnetic materials. For this reason, we can say that in order for a nucleus to be used on an electromagnet it must be magnetizable.