Increases in life expectancy in the United States during the twentieth century were due primarily to
a. the control of childhood and infectious diseases.
b. the fitness boom.
c. increased use of vitamin supplements.
d. the defeat of chronic illness.

A. the control of childhood and infectious diseases.

Explanation: Life expectancy began to rise due to better sanitation and education in the twentieth century

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answer: a federal government has final authority on interstate/inter provincial  and international affairs, a confederation is one where the central/national government or authority is governing body what does not have final say over the same matters. hopefully this and i will try again if you don't like this answer : )

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