If the maximum amplitude of an amplitude modulated wave is \[25\text{ }V\] and the minimum amplitude is \[5\text{ }V,\] the modulation index is:

• A. \[\frac{1}{5}\]
• B. \[\frac{1}{3}\]
• C. \[\frac{3}{2}\]
• D. \[\frac{2}{3}\]