What enabled Native American tribes to make treaties with U.S. Government?

A: The ability of leaders to communicate in English
B: The wealth of an individual tribes
C: Their understanding of American law****
D: Their stories as Sovereign nations

Why does the US negotiate treaties with other nations?
A. to claim rights to new lands
B. to declare hostile intentions
C. to gather info about policies
D. to make legally binding agreements***

are my answers right? for clarification my answers are C and D