The correct answer is "C".
Compared to the other 3 options, which are all part of the foreign policy executed by the United States Federal government, the Affordable Care Act nicknamed as "Obamacare", is a domestic policy act which represented the most significant expansion of health coverage since Medicare in 1965. This policy aimed to reduce the percentage of uncovered people in the country, as prior to the signing of the Law, this group was nearly reaching half of the population in 2014.