The correct answer is C. 1998.
The Good Friday Agreement, also known as the Belfast Agreement, was a major turning point in the Northern Ireland conflict. It was signed on Good Friday, April 10, 1998, by the British and Irish governments, and by the political parties in Northern Ireland. The agreement was designed to end the violence and establish a power-sharing government in Northern Ireland.
The Ulster Unionist Party (UUP) was the largest party in Northern Ireland at the time of the Good Friday Agreement. The UUP was initially opposed to the agreement, but it eventually endorsed it after securing a number of concessions from the British and Irish governments.
The UUP’s endorsement of the Good Friday Agreement was a major breakthrough in the Northern Ireland peace process. It helped to pave the way for the establishment of a power-sharing government in Northern Ireland and the end of the violence.
The other options are incorrect. Option A, 1993, is the year that the Downing Street Declaration was issued. The Downing Street Declaration was a joint statement by the British and Irish governments that set out a framework for peace in Northern Ireland. Option B, 1986, is the year that the Anglo-Irish Agreement was signed. The Anglo-Irish Agreement was a treaty between the British and Irish governments that established a framework for cooperation on Northern Ireland. Option D, 1990, is the year that the Framework Document was published. The Framework Document was a joint paper by the British and Irish governments that set out a framework for a new political settlement in Northern Ireland.