题目对应教授所说：Today we're going to focus on the Iroquois and Hooray peoples. They lived in the northeastern great lakes region of North America. Now, back then, their lives depended on the natural resources of the forests, especially the birch tree. 其中back then 说明接下来的内容是本节课的重点，即森林资源对于 Iroquois and Hooray peoples 的重要性，对应 C。

答案: C