The figure shows a plot of photo current versus anode potential i'or a photosensitive surface for three difrerent radiations. Which one of the following is a correct statement?

• A

  Curves a and b represent incident radiations of different frequencies and different intensities.

• B

  Curv'es a and b represent incident radiations of the same frequency but of different intensities

• C

  Curves b and c represent incident radiations of different frequencies and different intensities

• D

  Curves b and c represent incident radiations of the same frequency having the same intensity