The equivalent conductance of $1\mathrm{M}$ benzoic acid is $12.8\mathrm{o}\mathrm{h}{\mathrm{m}}^{-1}\mathrm{c}{\mathrm{m}}^2$ and if the conductance of benzoate ion and ${\mathrm{H}}^{+}$ ion at infinite dilution are $42$ and $288.42\mathrm{}\mathrm{o}\mathrm{h}{\mathrm{m}}^{-1}\mathrm{c}{\mathrm{m}}^2$ respectively. Then its degree of dissociation is

• A

  $0.039\mathrm{\%}$
• Correct answer
  B

  $3.9\mathrm{\%}$
• C

  $0.35\mathrm{\%}$
• D

  $39\mathrm{\%}$

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