Final answer:
The number of fish released by school fish when attacked cannot be determined based on the given information.
Step-by-step explanation:
In the context of the question, the term 'school fish' refers to fish that swim together in a group or school. When school fish are attacked, they release other fish from the end of the trail. Based on the information provided, it is not possible to determine the exact number of fish that will be released. Therefore, none of the options (5th, 10th, 15th, 20th) can be considered as the correct answer to the question.