What type of unit cell from following is common to all seven types of crystal systems?

What is atomic radius of an element if it crystallises in BCC structure with edge length of unit cell 287 pm?

A metal crystallises in bcc structure with edge length $4 \times 10^{-8}$. If density of unit cell is $10 \mathrm{~g} \mathrm{~cm}^{-3}$. What is its molar mass?

n-type of semiconductor is formed when