Packing fraction in $2-\mathrm{D}$ hexagonal arrangement is

Give the correct order of initials $\mathrm{T}$ (true) or $\mathrm{F}$ (False) for following statements :

I. In an anti-fluorite structure anions form $\mathrm{FCC}$ lattice and cations occupy all tetrahedral voids.

II. If the radius of cations and anions are $0.2\stackrel{°}{\mathrm{A}}$ and $0.95 \stackrel{°}{\mathrm{A}}$ then coordinate number of cation in the crystal is $4 .$

III. An atom/ion is transferred from a lattice site to an interstitial position in Frenkel defect.

IV. Density of crystal always increases due to substitutional impurity defect.