What social changes were most responsible for the 30-year increase in American life expectancy over the 20th century?

answer is given below

Explanation:

Social change refers to any significant change in behavior patterns and cultural values and norms over time

so for 30 year in america they are as

Better Sanitation                Very little to do with the medical innovation               Better distribution of wealth through eight working hour in a day GI Bill                            Tax on the personal income                                      

these were the some change

What the question i don't get it do u mean what she needs to do to auctually become one