In amplitude modulation of waves, the maximum amplitude is 30 mV and minimum amplitude is 5 mV, then the modulation index is

• A

  $\frac{4}{7}$
• B

  $\frac{3}{7}$
• Correct answer
  C

  $\frac{5}{7}$
• D

  $\frac{2}{7}$

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