The correct answer is (a) Scotland.
Scotland held the world’s first referendum on same-sex marriage on 18 September 2014. The referendum was held alongside the Scottish independence referendum, and asked voters whether they supported the introduction of same-sex marriage in Scotland. The referendum was approved by 55.8% of voters, with a turnout of 84.5%.
The other options are incorrect. Ireland held a referendum on same-sex marriage on 22 May 2015, and England and Wales held a referendum on same-sex marriage on 5 May 2013. The U.S.A. has never held a national referendum on same-sex marriage, although several states have held their own referendums on the issue.
Scotland’s referendum was a landmark moment in the fight for same-sex marriage. It was the first time that a country had asked its citizens to vote on the issue, and the result was a resounding victory for equality. The referendum paved the way for the introduction of same-sex marriage in Scotland in 2014, and it has since been used as a model by other countries that are considering introducing same-sex marriage.