Final answer:
Japan is highlighted in discussions about age distribution because it is the fastest-graying nation, with a rapidly increasing proportion of elderly individuals and a declining young population, leading to economic and labor challenges.
Step-by-step explanation:
Japan is mentioned in the age distribution section because A. it is the fastest-graying nation in the industrial world. This means that the proportion of elderly people in the population is increasing at a rapid pace. The demographic dynamics indicate that Japan has a declining population due to a negative population growth trend. Furthermore, Japan is facing a labor shortage in many sectors as a result of a shrinking pool of young people entering the workforce. Population statistics show that Japan is experiencing a serious decline in numbers, which pertains to challenges in maintaining the standard of living, providing social services, and sustaining economic productivity.