Silicon doped with gallium forms

Which of the following is a network crystalline solid?

The number of atoms in $$2.4 \mathrm{~g}$$ of body centred cubic crystal with edge length $$200 \mathrm{pm}$$ is (density $$=10 \mathrm{~g} \mathrm{~cm}^{-3}, \mathrm{~N}_A=6 \times 10^{23}$$ atoms$$/ \mathrm{mol}$$)

1 mole of $$\mathrm{NaCl}$$ is doped with $$10^{-5}$$ mole of $$\mathrm{SrCl}_2$$. The number of cationic vacancies in the crystal lattice will be