If the atomic radius of aluminum is r, what is its unit cell volume?

• A. \({\left( {\frac{{2r}}{{\sqrt 2 }}} \right)^2}\)
• B. \({\left( {\frac{{4r}}{{\sqrt 2 }}} \right)^3}\)
• C. \({\left( {\frac{{2r}}{{\sqrt 3 }}} \right)^3}\)
• D. \({\left( {\frac{{4r}}{{\sqrt 3 }}} \right)^3}\)