Answer:
24 students that have used a vaping product at least once
Explanation:
Based on the scenario described we can say that the who in this study would be the 24 students that have used a vaping product at least once. That is because the entire study is focused around individuals who have used vaping products, therefore since only a select population were chosen to be part of the study we need to determine and target which of this selected sample of students have used vaping products and that will be the "who" in the study. Which in this scenario, are 24 students.