A. A group of hunters following a migrating herd . This would be a hunter gatherer group, not a civilization.
B. A large group of people living in a city . This is the best option, it is more than one person in an almost permanent location.
C. A migrating family that gathers plants . Migrating, this means they are always on the move.
D. A single person living in a cave. No, a civilization has to be made up of more than one person.
I hope this helps! :)