The magnetic needle of a magnetic compass is made up of $\qquad$ .

The most appropriate magnetization $M$ versus magnetising field $H$ curve for a paramagnetic substance is

Consider the following two statements $A$ and $B$ and identify the correct choice in the given answers.
$A$. Paramagnetism is explained by domain theory.
$B$. Susceptibility of a diamagnetic substance is independent of temperature.

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

Assertion $(A)$: Electromagnets are made of soft iron.
Reason $(R)$: Coercivity is small for soft iron.

Magnetic susceptibility for a paramagnetic and diamagnetic material is respectively