If 'a' is the edge length of a unit cell, then correct option(s) is/are:

• A

  $\text{ for simple cubic lattice, radius of metal atom }=\frac{\mathrm{a}}{2}$

• B

  $\text{ for b. c. c. lattice, radius of metal atom }=\frac{\sqrt{3}\mathrm{a}}{2}$

• C

  $\text{ for f. c. c. lattice, radius of metal atom }=\frac{\mathrm{a}}{2\sqrt{2}}$

• D

  options (2) and (3) are incorrect.