The correct statement(s) for cubic close packed (ccp) three dimensional structure is/are:

The correct options are
B The efficiency of atom packing is 74%.
C The number of octahedral and tetrahedral voids per atom are 1 and 2, respectively.
D The unit cell edge length is $2\sqrt{2}$ times the radius of the atom.
The middle layers will have 12 nearest neighbours. The top-most layer will have 9 nearest neighbours.
$4r=a\sqrt{2},$ where ‘a’ is edge length of unit cell and ‘r’ is radius of atom. Thus $a=2\sqrt{2}r$.