Final answer:
The question addresses collective behavior in Social Studies, and the correct answer is option b, where a group of people assemble based on shared interest to hear an author speak, representing a typical example of collective behavior.
Step-by-step explanation:
The subject of this question falls under Social Studies, specifically addressing the concept of collective behavior. When we look at the provided options to identify an example of collective behavior, we should understand that this term refers to actions taken by a group of people that are often spontaneous and typically violate the norms of the situation. The correct answer is option b. A group of people interested in hearing an author speak. This is because it involves a collective interest and behavior that result in the group assembling to listen to the author, making it a phenomenon that occurs in a social setting where norms are generally followed, but the spontaneous assembly based on common interest classifies it as collective behavior.