At $25\,^{\circ}C$,the molar conductance of a $0.1\, M$ aqueous solution of ammonium hydroxide is $9.54\, \Omega^{-1}\, cm^2\, mol^{-1}$ and at infinite dilution,its molar conductance is $238\, \Omega^{-1}\, cm^2\, mol^{-1}$. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is ............ $\%$

• A
  $40.800$
• B
  $2.080$
• C
  $20.800$
• D
  $4.008$