Answer:
It's an example of Demographic trends.
Explanation:
Demographic trend can be defined as the measurable change in the characteristics of a population over time e.g. Change in concentration of a particular ethnic group, age-group, occupation, religion, political view, sex ratio, etc.
Since the population in the U.S. is aging which means there will be an increased need for health care professionals in the future it indicates a demographic trend.
B: oral tradition I think hope this helps :)
