Which organization has line authority to oversee the management of multiple incidents being handled by separate incident command organizations?
a. area command
b. united command
c. multiagency command
d. joint command

Generally speaking, it would be a "Joint Command" that has line authority to oversee the management of multiple incidents being handled by separate Incident Command organizations, since in this scenario many different agencies are "joined" together. 

The answer is d.  the north had organized schools, whereas the south had few organized schools.