Final answer:
The provided information does not specifically address the 20 percent option (a) of older adults who are grandparents, but it highlights the significant increase in the elderly population and their improved health and financial status, which might indirectly affect grandparenthood trends.
Step-by-step explanation:
The question "What percentage of older adults are grandparents?" does not align with the provided data, which focuses on the aging population and its implications on health care and demography rather than specific details about grandparenthood statistics.
However, it is important to note the demographic shift towards an older population in the U.S. For instance, the aging U.S. population has seen a significant increase in elderly people over the past century, with those over 65 years of age making up a growing percentage of the overall population.
Moreover, life expectancy has risen, leading to increased numbers of people living into advanced age. According to the Boston University School of Medicine (2014), the number of centenarians in the United States has been one of the fastest-growing segments of the population.
Furthermore, today's young adults (approximately sixty-five to seventy-four years old) are generally healthier, happier, and more financially secure than in previous generations, likely affecting grandparenthood trends.
Despite this, the provided materials do not offer a direct answer to the percentage of older adults who are grandparents, thus no specific percentage can be accurately given to answer the multiple-choice question posted.