THAT it is a relative pronoun!
Hello. You did not show the text to which this question refers, which makes it impossible for it to be answered accurately. However, I will try to help you in the best possible way.
It is only possible to know the inference that the author made with the reading of the text. However, an inference is a conclusion, which can only be established through the analysis of facts and arguments, which trigger a conclusion, an opinion on the subject. In this case, to answer your question, you should look at how the author's arguments about the students' return lead to a conclusion that must be made on this subject.
Answer:
Foreign languages can you show us how to talk to people in different places for example if you learn Latin you will be able to talk to people in Mexico and places like Italy and such but if you are in Russian you can go and speak to people in Russian so if you are in different languages you can learn how to speak to people in different countries.