“China’s achievements in health care across the twentieth century are remarkable. With an estimated average life expectancy of only thirty years in 1900, it is no wonder that China was denigrated as the ‘sick man of Asia.’ By the end of the century in 2000, however, China’s life expectancy had more than doubled, to an estimated seventy-one years. A comparison with the United States highlights the nature of China’s achievements. China was seventeen years behind America’s life expectancy in 1900 (30 versus 47) and that gap actually widened to twenty-five years (44 versus 69) by mid-century. Yet by 2000, the gap had narrowed to only six years, with China’s average life expectancy at 71 and the United States’ life expectancy at 77. The weak progress in China in the first half of the century, 1900–1950, was undoubtedly related to the political chaos, foreign invasion, and civil war that characterized China’s history in that period. On the other hand, the marked acceleration in health care improvements in the second half of the century, 1950–2000, was achieved due to political stability and strong government commitment to equitable health policies. While not dismissing the usefulness of traditional Chinese medicine, there is strong evidence that the application of modern medical science through hospitals and field-based health-systems operated by well-trained health professionals has a major impact on health outcomes. Social factors are also at work, perhaps the most important of these being the development of universal literacy and the increase in gender equality.” Lincoln Chen and Ling Chen, historians, “China’s Exceptional Health Transitions,” scholarly article, 2014 Question The changes in life expectancy in China described in the second paragraph are most likely attributable to which of the following