Answer
a) red source energy is less than green source energy
b) II
Work Step by Step
(a) We know that $E=hf$. This equation shows that the energy of the radiation is directly proportional to the frequency, therefore $E_{red}\lt E_{green}$.
(b) We know that the best explanation is option (II) -- that is, the red-source photons have less energy than the green-source photons because they have a lower frequency. The wattage of the source doesn't matter.
