The feud between the Montagues and the Capulets is the cause of Romeo and Juliet's deaths, and probably their romance as well. If there were no feud, the two families would have moved in the same circles, and Romeo and Juliet would have known each other all their lives.
I would say the correct answer is that has an undetermined answer.
If a subject has been thoroughly covered, then there is no need for this researcher to do it all over again. If it's impossible to answer, there is no need to try. If it can be answered easily, then it doesn't really require a research. This leaves us with the last option, because a researcher might want to try and determine the answer.
