35. Which is the incorrect statement

a. FeO_0.98   has non stoichiometric metal deficiency defect

b. Density decreases in case of crystals with Schottky’s defect

c. NaCl is insulator silicon is semiconductor silver conductor quartz is piezo electric crystal

d. Frenkel defect is favoured in those ionic compounds in which sizes of cation and anions are almost equal

Ans. a.