The wavelengths of each type of electro-magnetic radiation are different. The energy content of each type is directly related to the wavelength (recall that SHORT wavelengths are more energetic than LONG wavelengths). Thus, the answer cannot be B or D. It turns out that the frequency of different types of radiation is also different but that the PRODUCT OF WAVELENGTH AND FREQUENCY is a constant. That constant is the SPEED OF LIGHT. Thus, the answer is A.