Which statement best describes the impact of discovery of gold on american indian territory in the 1850s and 1870s

The correct answer for this question is "C. War broke out among American Indian groups when warring chiefs signed new treaties with the government." 

The statement that best describes the impact of discovery of gold on American Indian territory in the 1850s and 1870s is that war broke out among American Indian groups when warring chiefs signed new treaties with the government
Here are the following choices:
A. Indian groups when warring chiefs signed new treaties with the government.
B. War broke out when white settlers pressured the government to take the land from American Indians.
C. War broke out among American Indian groups when some groups sold their land to the government.
D. War broke out when white settlers tried to buy land from warring American Indian groups.