Which defect leads to an increase in the density of a solid?

If $AgCl$ is doped with $1 \times 10^{-4}$ mole percent of $CdCl_2$,the number of cation vacancies (in $mol^{-1}$) is

When $CaCl_2$ is added to $AgCl$ crystal,the defect introduced is

Schottky defect defines imperfection in the lattice structure of a

When $Fe_{0.93}O$ is heated in the presence of oxygen,it converts to $Fe_2O_3$. The number of correct statement$(s)$ from the following is:
$A.$ The equivalent weight of $Fe_{0.93}O$ is $\frac{\text{Molecular weight}}{0.79}$.
$B.$ The number of moles of $Fe^{2+}$ and $Fe^{3+}$ in $1 \text{ mole}$ of $Fe_{0.93}O$ is $0.79$ and $0.14$ respectively.
$C.$ $Fe_{0.93}O$ is metal deficient with a lattice comprising of a cubic closed-packed arrangement of $O^{2-}$ ions.
$D.$ The $\%$ composition of $Fe^{2+}$ and $Fe^{3+}$ in $Fe_{0.93}O$ is $85\%$ and $15\%$ respectively.

If $NaCl$ is doped with $10^{-3} \, mol \%$ of $SrCl_{2}$,what is the concentration of cation vacancies?