Which event sparked the start of the Yakama Wars? US soldiers assassinated Chief Kamiakin.
Yakamas attacked settlers to keep diseases off the reservation.
US soldiers killed a group of Yakamas who left the reservation.
Yakamas killed an agent from the Bureau of Indian Affairs.

Answer is (d). Yakamas killed an agent from the Bureau of Indian Affairs.

Explanation:

In October, 1855, the conflict escalated to the point of war. Several Yakamas killed an agent from the Bureau of Indian Affairs. The Indian agent had come onto Yakama lands to investigate the rumored death of miners. The Yakama knew that the death of the agent would lead to conflict, so they began to prepare for war.

as general terms,  indian territory,  the indian territories, or  indian country  describe an evolving land area set aside by the  united states government  for the relocation of  native americans  who held  aboriginal title  to their land. in general, the tribes ceded land they occupied in exchange for  land grants  in 1803. the concept of an indian territory was an outcome of the 18th- and 19th-century policy of  indian removal. after the  civil war(1861–1865), the policy of the government was one of  assimilation.