Iron exhibits bcc structure at room temperature. About $900^oC$, it transforms to fcc structure. The ratio of density of iron at room temperature to that at $900^oC$ (assuming molar mass and atomic radii of iron remains constant with temperature) is

Question

( A ) $\frac{4 \sqrt{3}}{3 \sqrt{2}}$
( B ) $\frac{1}{2}$
( C ) $\frac{3 \sqrt{3}}{4 \sqrt{2}}$
( D ) $\frac{\sqrt{3}}{\sqrt{2}}$