'प्राथमिक समूह' (primary group) की समाजशास्त्रीय अवधारणा को किसने प्रतिपादित किया था?

Which of the following is considered the primary and basic social group in society?

A researcher is comparing the influence of family and student councils on learners' values. Which distinction between social groups is most relevant for understanding the nature of these influences?