In "The Book of Unknown Americans," paragraph 10 primarily serves to emphasize the tension between the old and new cultures. It explores the characters' struggles with their identities as they navigate their lives in a new country, illustrating the challenges they face as they try to reconcile their heritage with the realities of living in America. This tension is a recurring theme in the book, impacting relationships and the overall narrative of immigrant experiences.
So, the correct answer would be: It emphasizes the tension between the old and new cultures.