Which among the following is $NOT$ an amorphous solid?

Given below are two statements. One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Sharp glass edge becomes smooth on heating it up to its melting point.
Reason $R$: The viscosity of glass decreases on melting.
Choose the most appropriate answer from the options given below.

Which one of the following elements on doping with germanium, makes it a $p$-type semiconductor?

How many of the following compounds show ferrimagnetism?
$Fe_3O_4; MgFe_2O_4; NiFe_2O_4; MnO; CrO_2$

Which crystal system exhibits the highest degree of asymmetry?

Explain Ferrimagnetism.