The death rates in the United States decreased more than 40 percent from 1930 to 2015. Which factor could have contributed to this decrease? OA
increased food insecurity
OB
better medical facilities and treatments
C.
decreased farmland
OD
refusal of vaccines
E
illiteracy

The correct answer is - B. better medical facilities and treatments.

In the past century, the life expectancy in the United States have increased significantly, in fact it is almost doubled. The death rates have decreased for around 40% and the biggest reason for this trend are the advancements in the medical field. The medical facilities and treatments have improved significantly. The technological advancements contributed to the medical field a lot, made it much more efficient, and because of that the prevention of diseases, curing, and the saving of lives have skyrocketed, resulting in much better, healthier,and longer life of the population

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Explanation:

the correct option is option d

you know they are heterozygous for a trait because they have it as jj or jj.