This graph shows life expectancy in the United States. A graph titled Life Expectancy in the U S. The x axis shows the years 1960 to 2010. The y axis shows life expectancy, from 64 to 80. The line starts at under 70 in 1960, 71 in 1971, 73 in 1980, 75 in 1990, 77 in 2000, 78 in 2010.

Which factor best explains why the graph changes from 1990 to 2010?
A. New technology protects soldiers from risky reconnaissance missions.
B. New technology allows farmers to grow genetically modified crops.
C. New technology allows us to find and use new energy sources.
D. New technology has improved medical imaging and surgery.