What Has Been the Most Important Factor in Reducing the Number

What has been the most important factor in reducing the number of older adults living below the poverty line in the United States of America?

A) the raising of the mandatory retirement age for workers in the USA.
B) the creation of government-funded programs, such as Social Security
C) the establishment of earned income retirement accounts (EIRAs) that are tax shelters until a person reaches the age of 67.5 years.
D) new federal regulations that provide financial incentives to companies whose workforce includes at least 10% senior citizens.