A solid $\left(\mathrm{A}\mathrm{B}\right)$ has rocksalt structure. If the edge length is $400\mathrm{ }\mathrm{p}\mathrm{m}$ and the radius of the cation is $80\mathrm{ }\mathrm{p}\mathrm{m}$ , then the radius of the anion is

• A

  $100$ $\mathrm{p}\mathrm{m}$
• Correct answer
  B

  $120$ $\mathrm{p}\mathrm{m}$
• C

  $250$ $\mathrm{p}\mathrm{m}$
• D

  $325$ $\mathrm{p}\mathrm{m}$

Hence, the correct answer is option: 'B'.