Answer: a) the nation he grew up
Explanation:
According to the situation in question,Manne is displaying about his nation as the base for social group. He interacts, socializes and shops with immigrants, this shows that he can relate with them socially which is feature he got from nation as where he grew up.
Other options are incorrect because religion , family or school are not responsible for developing socialization between people and Manne.
Thus, the correct option is option(a).