The answer is (d) the quality of health care that exists today was not available in 1900. While increases in real GDP since 1900 do reflect some of the improvements in the standard of living, they do not capture all of the improvements that have been made. One major area of improvement that is not reflected in GDP is the quality of health care. In 1900, many medical procedures that are now routine were not available, and overall life expectancy was much lower. As a result, even if real GDP has increased since 1900, the overall standard of living has improved much more than GDP alone would suggest.