Select the correct statements:

In bec structure, $r^{+}+r=\frac{\sqrt{3}}{2}a$

Hence, for $\text{CsCl},{\text{r}}_{\text{c}}+{\text{r}}_{\text{a}}=\frac{\sqrt{3}}{2}\text{a}$

$\therefore \left(A\right)$ is correct.

Since, NaCl crystallizes in fce structure

$\therefore 2{\text{r}}_{\text{c}}+2{\text{r}}_{\text{a}}=$edge length of the unit cell

Hence, $r_c+r_b=\frac{1}{2}$

$\therefore \left(B\right)$ is correct.

Since packing fraction of a bec unit cell is 0.68

$\therefore$ Void space =1-0.68=0.32

$\therefore \left(C\right)$ is not correct.

In fce unit ceil, PF=74%

$\therefore \text{VF}=100-74=26\text{\%}$

$\therefore \left(D\right)$ is correct.

Hence, (A),(B) and (D) are the correct answers.