If a the length of the side of a cube, the distance between the body centered atom one corner atom in the cube will be -

Question

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