Answer:
RADIO WAVES
Step-by-step explanation:
As we know that energy of electromagnetic waves and its wavelength is related by the formula
![E = (hc)/(\lambda)](https://img.qammunity.org/2019/formulas/physics/college/xxwng06dnfxbga3xhvyh3zrgh2lrjuj8js.png)
so here as we can see that energy is inversely depends on wavelength so for the longest wavelength the energy is least.
So here we know that least energy electromagnetic waves are Radio waves.
So the longest wavelength must be corresponding to least energy electromagnetic waves
So here correct answer for longest wavelength will be
RADIO WAVES