The Sioux were promised these annuities in exchange for stopping the violence. When they did not get these annuities then they caused violence again.
Explanation:
The US government signed two treaties with the Sioux in exchange for large portions of the Minnesota Territory in 1851. The Treaty said that the land would be given in exchange for compensation in the form of annuity cash payments and trade goods.
The problem was that the organization was poor and corrupt and the resources did not get to the Sioux. Things got worse when Minnesota entered the Union and the government repossessed half of the territory and gave it to white settlers. All of this was the perfect storm for the Sioux uprising in 1862.
The treaty violations by the United States and late and unfair annuities by the Indian Agents had caused increasing problems on hunger and poverty amongst the settlers and the Native Americans. Many Dakotan traders had demanded that annuities must be paid or else they will stopped providing goods on credit basis.
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 B is because it wasn't the polling that contributed to the act, but what the polls showed which is C.
