Due to $Frenkel$ defect,the density of ionic solids

While writing the formula of ferrous oxide,it is written as $(FeO)$,because it is

When electrons are trapped into the crystal in anion vacancy,the defect is known as

Why does white $ZnO_{(s)}$ become yellow upon heating?

Which of the following compounds exhibits metal deficiency defect?

$A$ metallic solid undergoes Frenkel defect. Its original mass,volume and density are $M_0$,$V_0$ and $D_0$ respectively. After Frenkel defect the mass,volume and density are $M$,$V$ and $D$ respectively. The variations of $M$,$V$ and $D$ after Frenkel defect are