C. Complex social institutions.
I guess, the first thing that must be done in a settlement to be considered a civilization is order in the society. A ruler or form of government is needed. After the accomplishments on the political and social aspects. It is already a civilization. It is then, when the civilization needs protection against invaders. So A is not the answer. B cannot be cuz this "early" civilization is not possible to know about monarchies when it hasn't even set a form of getting government and it has just settled and populated. If there's not ruler, there's no such thing as territory. So, it is not D but C :v
