The answer that makes the most sense to me is A. human environment interaction because they're studying what the logging industry, which is a human action, affects the rainforest, which is an environment.
This is both true and untrue. It's true because knowing the language you can get a job and work in a foreign place and eventually become a naturalized citizen of the place. It is untrue because the person there should also know the customs and culture and not just the language, because lack of knowing these can lead to alienation and depression.
At the time, the US was trying to practice Isolationism. They refrained form signing the treaty of versailles, and thus were never involved in the League of Nations.
It could make you proud to be connected to that nation, and when people think of you they also think of your nation that you are connected with.
