The legalization of same-sex marriage in 2015 illustrates

A) the impact that an interest group can have through lobbying Congress.
B) the impact that an interest group can have through a litigation strategy.
C) the impact that an interest group can have through Super PACs.
D) the impact of iron triangles on the policy making process.

The legalization of same-sex marriage in 2015 was a result of litigation strategy pursued by interest groups such as the American Civil Liberties Union (ACLU) and Human Rights Campaign (HRC). These interest groups filed lawsuits and worked through the court system to challenge existing laws and policies, leading to the Supreme Court's landmark decision in Obergefell v. Hodges. While interest groups can also use lobbying and Super PACs, in this case, it was the litigation and legal strategy that had the greatest impact. Iron triangles typically refer to the relationship between interest groups, Congress, and government agencies, and it doesn't directly apply to the legalization of same-sex marriage.