What is the total number of different types of unit cells present in triclinic crystal system?

Calculate molar mass of an element having density $8.6 \mathrm{~g} \mathrm{~cm}^{-3}$ if it forms bec structure $\left[\mathrm{a}^3 \times \mathrm{N}_{\mathrm{A}}=22.0 \mathrm{~cm}^3 \mathrm{~mol}^{-1}\right]$

Calculate the radius of metal atom if it forms bec unit cell having edge length 530 pm.

Which from the following statements is NOT true regarding crystalline solid?