Answer: D. Economic prosperity increased investment in and access to new medical technologies and treatments.
Step-by-step explanation:
After the Second World War, massive investment in the economy by the government led to precedented levels of growth in the economy of the United States.
This growth and prosperity allowed for increased investment in many sectors including health. This led to better medicine and healthcare techniques and equipment which meant that people were cured of more illnesses and lived longer with longer life expectancy which is what the table above is showing.