Which type of magnets are used in extremely fast trains that run on magnetic levitation?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$. Consider a ferromagnetic material:
Assertion $(A)$: The individual atoms in a ferromagnetic material possess a magnetic dipole moment and interact with one another in such a way that they spontaneously align themselves forming domains.
Reason $(R)$: At high enough temperature, the domain structure of a ferromagnetic material disintegrates. Thus, magnetization will disappear at a high enough temperature known as the Curie temperature.
In the light of the above statements, choose the correct answer from the options given below:

Which one of the following characteristics is not associated with a ferromagnetic material?

Which of the following statements is true in respect of diamagnetic substances?

Which of the following is most suitable for the core of electromagnets?

Why is the magnetic susceptibility of diamagnetic materials negative? Explain.