Compounds with low coordination numbers of cations and anions exhibit Frenkel defects because the compound has ................

Given below are two statements.
Statement $I:$ Frenkel defects are vacancy as well as interstitial defects.
Statement $II:$ Frenkel defect leads to colour in ionic solids due to presence of $F$-centres.
Choose the most appropriate answer for the statements from the options given below:

$A$ silicon specimen is made into a $p-$type semiconductor by doping,on an average,one indium atom per $5 \times 10^7$ silicon atoms. If the number density of atoms in the silicon specimen is $5 \times 10^{28} \ \text{atoms} \ m^{-3}$,then the number of acceptor atoms in silicon per cubic centimeter will be

Use the appropriate symbols $T$ (True) or $F$ (False) for the following statements regarding defects in solids:
$(1)$ Frenkel defect arises due to the arrangement of cations and anions with a very small difference in size.
$(2)$ Frenkel defect can be called a dislocation defect.
$(3)$ $F$-centers arise due to the migration of electrons released from metal atoms into the crystal lattice.
$(4)$ Physical properties of the crystal do not change due to Schottky defect.

Which of the following ionic crystals exhibits Frenkel defect?

Non-stoichiometric cuprous oxide,$Cu_{2}O$ can be prepared in the laboratory. In this oxide,the copper to oxygen ratio is slightly less than $2:1$. Can you account for the fact that this substance is a $p$-type semiconductor?