In general,for soaps,the concentration of surfactant at $CMC$ is around $mol \ L^{-1}$.

• A
  $10^{-4}$ to $10^{-3}$
• B
  $10^{-4}$ to $10^{-1}$
• C
  $10^{-7}$ to $10^{-4}$
• D
  $10^{-4}$ to $10^{+2}$