Yeah, I think that question is a bit too open-ended, and would result in a tonne of marks last unless they had some revolutionary marking system.
I'm not too sure about de Broglie, perhaps the fact that the mass deficit is being converted into momentum, hence kinetic energy, due to the newfound nature of all matter? Seems like a bit of a stretch to say the least. I'd likely focus it around stars, nuclear power (both fusion and fission) and our overall understanding of matter via particle accelerators (i.e. the discovery of quarks, leptons and hadrons and consequent discovery of force carriers)