Final answer:
Collective behavior refers to actions taken by a group of people for a common purpose, like a group interested in hearing an author speak, demonstrating a shared intent. Collective nouns can take a singular or plural form depending on the group's actions.
Step-by-step explanation:
The term collective behavior refers to actions taken by a group of people that come together for a common purpose or activity. In the context of the given options, the best example of collective behavior would be b. A group of people interested in hearing an author speak.
This scenario demonstrates a group that has assembled for the specific intent to engage in the same activity, namely listening to an author, which constitutes collective behavior. The other options do not represent collective behavior as precisely because they may not involve a cohesive group action or shared common intent.
Options such as a soldier questioning orders or going shopping with a friend denote individual rather than collective behavior. Furthermore, collective nouns like the band and team can take a singular or plural pronoun based on whether the group is acting as a single unit or individually, and the same principle applies to verb agreement.