Final answer:
Membership in a crowd is based on proximity, which refers to physical closeness and regular contact with individuals.
Step-by-step explanation:
The membership in a crowd is based on proximity. Proximity refers to the physical closeness or regular contact with individuals. According to research, you are more likely to become friends with people you have regular contact with, such as people who live in your dorm, apartment building, or immediate neighborhood. Proximity provides the opportunity to get to know others and form relationships.