If the traveler chooses N at stop 5, which one of the following could be an accurate list of the airlines she chooses...

I got this question right because I deduced that since N is 5th then L or M cannot be 4th based on rule #4 and not N based on rule #1. This leaves O as the only option. I eliminated all the answer choices that did not have O as second and tested the last two... was this just a lucky guess then?