Among the Later Mound Builders of North America, Cahokia Was

Among the later mound builders of North America, Cahokia was:

A) absolutely unique; there are no other large mound-building sites
B) the only large mound site to show clear evidence of contact with the complex civilizations of Mesoamerica to the south
C) not the largest but the first of the urban-like settlements
D) by far the largest but not the only impressive, densely settled, mound-building community