Which of the following best describes the main purpose...

Câu hỏi: Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.
People are living longer and, in some parts of the world, healthier lives. This represents one of the crowning achievements of the last century, but also a significant challenge. Longer lives must be planned for. Societal aging may affect economic growth and lead to many other issues, including the sustainability of families, the ability of states and communities to provide resources for older citizens, and international relations. The Global Burden of Disease, a study conducted by the World Health Organization, predicts a very large increase in age-related chronic disease in all regions of the world. Dealing with this will be a significant challenge for all countries' health services.
Population aging is driven by declines in fertility and improvements in health and longevity. In more developed countries, falling fertility beginning in the early 1900's has resulted in current levels being below the population replacement rate of two live births per woman. Perhaps the most surprising demographic development of the past 20 years has been the pace of fertility decline in many less developed countries. In 2006, for example, the total fertility rate was at or below the replacement rate in 44 less developed countries.
One central issue for policymakers in regard to pension funds is the relationship between the official retirement age and actual retirement age. Over several decades in the latter part of the 20th century, many of the more developed nations lowered the official age at which people become fully entitled to public pension benefits. This was propelled by general economic conditions, changes in welfare philosophy, and private pension trends. Despite the recent trend toward increased workforce participation at older ages, a significant gap between official and actual ages of retirement persists. This trend is emerging in rapidly aging developing countries as well. Many countries already have taken steps towards much-needed reform of their old-age social insurance programs. One common reform has been to raise the age at which workers are eligible for full public pension benefits. Another strategy for bolstering economic security for older people has been to increase the contributions by workers. Other measures to enhance income for older people include new financial instruments for private savings, tax incentives for individual retirement savings, and supplemental occupational pension plans.
As life expectancy increases in most nations, so do the odds of different generations within a family coexisting. In more developed countries, this has manifested itself as the 'beanpole family,' a vertical extension of family structure characterized by an increase in the number of living generations within a lineage and a decrease in the number of people within each generation. As mortality rates continue to improve, more people in their 50's and 60's will have surviving parents, aunts, and uncles. Consequently, more children will know their grandparents and even their great-grandparents, especially their great-grandmothers. There is no historical precedent for a majority of middle-aged and older adults having living parents.
Which of the following best describes the main purpose of the author in the passage?
A. To present a synopsis of the causes and effects of the aging population.
B. To provide an overview of the drawbacks of the world's aging population.
C. To suggest some effective solutions to deal with the rapid increase of the aging population.
D. To prove the significant contribution of the aging population to the world economy.