The edge lengths of the unit cells in terms of the radius of supheres consituting fcc, bcc and simple cubic unit cell are respectively. ..
A. `2 , sqrt2r ,(4r)/sqrt3 , 2r`
B. `(4r)/sqrt3 , 2sqrt2, 2r`
C. `2r, 2sqrt(2r) , (4r)/sqrt3`
D. ` 2r, (4r)/sqrt3 , 2sqrt(2r)`