समाजशास्त्र में परिभाषित प्राथमिक समूहों (primary groups) की निम्नलिखित में से कौन सी एक भौतिक विशेषता या आवश्यक गुण नहीं है?

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?