Why do we jump straight to E in the explanation.

Hello @nimakian801, I'll give you a bit more detail here. However, I also looked over the other answer choices and didn't immediately choose S, so don't worry if you had to do the same. The key to understanding that S is the issue comes from the eliminations that we can make while diagramming the rules. G - L - F tells us that neither L nor F can be in year 601. H must be in 604 or 605, and therefore it cannot be in 601. So, who remains to fill the two spots in 601? Only S, M, G. If S is in 604, not only does it push H into 605, it also guarantees that S and M are in 601. This leaves the two remaining years for L and F, in that order. It is perfectly fine if you have to test a few answer choices, but start with the one that you believe is going to have a big impact.