Simon Pokagon, a prominent Potawatomi leader and advocate for Native American rights, would have been most likely to oppose A. the Dawes Act.
The Dawes Act of 1887 aimed to assimilate Native Americans into American society by allotting them individual plots of land and reducing the collective land held by tribes. This legislation was generally detrimental to Native American communities, leading to significant loss of tribal land and undermining their cultural and social structures. Given Pokagon's efforts to preserve Native American identity and land rights, he would be opposed to such measures that aimed to individualize and undermine tribal sovereignty.
The other options, while significant, would have been less directly related to land allocation and the assimilation policies that characterized the Dawes Act.