Given the electric field of a complete amplitude modulated wave as $\vec E = \hat i E_c (1 + \frac{E_m}{E_c} \cos \omega_m t) \cos \omega_c t$,where the subscript $c$ stands for the carrier wave and $m$ for the modulating signal. The frequencies present in the modulated wave are:

• A
  $\omega_c$ and $\sqrt{\omega_c^2 + \omega_m^2}$
• B
  $\omega_c, \omega_c + \omega_m$ and $\omega_c - \omega_m$
• C
  $\omega_c$ and $\omega_m$
• D
  $\omega_c$ and $\sqrt{\omega_c \omega_m}$