The best answer is B) Measles was an unfamiliar disease to the Cayuse and thus they had no immunities to it.
Europeans had many diseases in their culture that, over generations, they had developed an immunity to. This lessened the severity of these diseases and even eliminated their danger to Europeans. People with no previous contact with the Europeans or their diseases, such as the Cayuse, did not have the same immunity, and thus were more greatly impacted by illnesses such as measles.
