Which of the following is an incorrect statement?

What type of crystal defect is indicated in the diagram below?
$Na^{+} \, Cl^{-} \, Na^{+} \, Cl^{-} \, Na^{+} \, Cl^{-}$
$Cl^{-} \, \Box \, Cl^{-} \, Na^{+} \, \Box \, Na^{+}$
$Na^{+} \, Cl^{-} \, \Box \, Cl^{-} \, Na^{+} \, Cl^{-}$
$Cl^{-} \, Na^{+} \, Cl^{-} \, Na^{+} \, \Box \, Na^{+}$

Missing of one monovalent cation and one monovalent anion from the crystal lattice is called

Which of the following molecular formula and type of defect are correct for the following statement?
"In $FeO$ crystal,some $Fe^{2+}$ ions are missing and the loss of positive charge is made up by the presence of $Fe^{3+}$ ions".

Explain the following term with a suitable example:
$(iii)$ Interstitials

The correct statement$(s)$ regarding defects in solids is(are):
$A$. Frenkel defect is usually favoured by a very small difference in the sizes of cation and anion.
$B$. Frenkel defect is a dislocation defect.
$C$. Trapping of an electron in the lattice leads to the formation of $F$-center.
$D$. Schottky defects have no effect on the physical properties of solids.