We have that according to the quantum theory from Planck, E=h*f where h is a constant and f is the frequency, thus B is correct. Let's analyze the other choices: The speed of light in vacuum is irrelevant to the energy of the photon. The instensity of a light source is correlated to the amount of photons in that light beam but it does not affect individual photons. Finally, if l is the wavelength of light, l*f=c. Substituting this in the first equation we see that photon energy is inversely proportional to the wavelength.