What is nationalism?

A. an individualist state of mind in which a person believes that a nation-state is dependent on their taxes
B. a collective state of mind in which people believe their primary duty and loyalty is to the nation-state
C. an individualist state of mind in which a person believes that a nation-state needs all its people to govern it
D. a collective state of mind in which people believe that their nation-state must work in accordance with other nations in order to thrive