Ithink it is plain or mound builders

the triple alliance. germany and austria-hungary were already allies by 1879 when, worried about a threat from russia, they formed the dual alliance. italy joined the group in 1882. there was a concern about a possible attack from france and the alliance needed powerful friends to defend it.

d.

the northwest territory became the most densely populated area in the u.s.

to protest slavery i would think it would be a