Coordination number of $Na^{+}$ ion in rock salt is

The radius of a calcium ion is $94 \text{ pm}$ and of the oxide ion is $146 \text{ pm}$. The possible crystal structure of calcium oxide will be

If three elements $X$,$Y$ and $Z$ crystallise in a $ccp$ lattice with $X$ atoms at the corners,$Y$ atoms at the cube centre and $Z$ atoms at the edges centre,the formula of the compound will be

Which of the following is correct for the crystal lattices mentioned below?

Which of the following expressions is correct for a sodium chloride $(NaCl)$ unit cell with edge length $a$?

In zinc blende structure,the coordination number of $Zn^{2+}$ ion is