Answer:
The correct answer to the question: Which animal introduced by European traders changed the lifestyles of American Indians living on the Great Plains, is: Horses.
Explanation:
Before the arrival of Europeans, the Great Plains Indian tribes tended to be small, rather sedentary and dedicated their lives to living their lives where they were settled, not moving long distances, not even to hunt. However, this picture changed when the horse was introduced and the tribes became used to them. The reason is that they opened up the horizon for tribes to move longer distances, hunt further away from their settled land and also, it allowed them to move, become more nomadic, rather than being static. This, in turn, also brought problems, as now tribes became more competitive, and aggressive towards each other, in their quest to gain more, and better lands, even to the expense of other tribes. This is why the answer is: The horse.
