Select the correct statements among following: (a = edge length of unit cell)

Nearest neighbour distance in NaCl $=\frac{\mathrm{a}}{2}$

Nearest neighbour distance in CaF₂ $=\frac{\mathrm{a}\sqrt{3}}{4}$

Nearest neighbour distance in Na₂O$=\frac{\mathrm{a}\sqrt{3}}{4}$
 

Nearest neighbour distance in CsCl $=\frac{\mathrm{a}\sqrt{3}}{2}$