Which from following is an example of two dimensional nanostructures?

Which from following combinations is an example for construction of n-type semiconductor?

Calculate the density of metal having molar mass $$210 \mathrm{~g} \mathrm{~mol}^{-1}$$ that forms simple cubic unit cell. $$\left(\mathrm{a}^3 \cdot \mathrm{N}_{\mathrm{A}}=21.5 \mathrm{~cm}^3 \mathrm{~mol}^{-1}\right)$$

Calculate the volume of unit cell if an element having molar mass $$56 \mathrm{~g} \mathrm{~mol}^{-1}$$ that forms bcc unit cells.

$$\left[\rho \cdot \mathrm{N}_{\mathrm{A}}=4: 8 \times 10^{24} \mathrm{~g} \mathrm{~cm}^{-3} \mathrm{~mol}^{-1}\right]$$