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.

the answer is migration

answer; taking up arms to defend the nation;