Final answer:
The correct answer for the example of collective behavior is 'b. A group of people interested in hearing an author speak', which refers to actions by a group with a sense of unity.
Step-by-step explanation:
The word that sounds like "gathered, like troops on a border," which is used to describe boating in calm waters is not the correct answer to the student's question about collective behavior. Instead, the correct answer to "Which of the following is an example of collective behavior?" is b. A group of people interested in hearing an author speak. Collective behavior refers to the actions taken by a group of people who are in the same place at the same time, where there is often a sense of unity or common identity among the participants.