Theory of Functionalism tends to observe and analyze society as a whole, as a functional organ formed by relationships between people and groups.
The theory of conflict argues that the division of society into bourgeois and working class generates conflicts because of their nature. Proposed by Karl Marx, the paper states that there will always be splits if this system remains in society. Thus, taking this into account, we can evaluate the statement as true, since capitalism has taken root in much of Western society.
I think Marx's theory is the best because explain better how we enter in conflict with each other and how life it is, for the poor people.