Schottky defect generally appears in

Which among the following statements is true about Schottky defect?

Iron crystallizes in $FCC$ with an edge length of $400 \ pm$. If it contains $0.1 \%$ Schottky defects, calculate its approximate density $[AW \text{ of } Fe = 56 \ g/mol]$. (in $g/cm^3$)

In which of the following is impurity defect observed?

Match List-$I$ with List-$II$.

List-$I$ (Defect)	List-$II$ (Examples)
$A$. Frenkel defects	$1$. $FeO$
$B$. Schottky defects	$2$. $NaCl$
$C$. Vacancy defects	$3$. $AgCl$
$D$. Metal deficiency defects	$4$. Crystals with vacant lattice sites

Frenkel defect is generally observed in which of the following?