I would say B because none of the others are even close.
Buddhism is a very peaceful religioun, I doubt it would be spread by violence
Culture. Food, behavior.
History. Common past.
Religion. Majority of shared faith.
Nationality. Belief in common ancestry.
Territory. Boundaries, like Lake Michigan.
Language. Common dialect.
Nation-state. An independent geopolitical unit of people having a common culture and identity.
