Which of the following is true for $CrO_2$?

Which from the following dopants is used in germanium to produce $p-$type semiconductor?

Choose the correct option for crystalline solids based on the following statements:
$(1)$ They do not have a sharp melting point.
$(2)$ They gradually soften upon heating.
$(3)$ They have an irregular three-dimensional arrangement.
$(4)$ They show a rapid change in volume upon heating.

What type of solid is silica?

Classify each of the following as being either a $p$-type or a $n$-type semiconductor:
$(i)$ $Ge$ doped with $In$
$(ii)$ $Si$ doped with $B$.

Explain paramagnetism and diamagnetism. Write a note on ferromagnetism. Explain antiferromagnetism.