The American attitude shifted in favor of rights for Native Americans. This is based on "Polls showed that Americans believed in rights for Native Americans". Why it's not A is because it wasn't the polling that contributed to the act, but what the polls showed which is C.
Andrew Jackson. The Manifest Destiny, being the goal of reaching "sea to shining sea," was a major goal for this president. He was the president who initiated the Lewis and Clarke expedition. Drop a thanks if this helped !
