Which major event involved the Council of Europe in 2017?

The correct answer highlights the Council of Europe's involvement with the Russian siege at a school in Beslan, which is significant for its longstanding focus on human rights issues. The Beslan school siege occurred in 2004, leading to a tragic loss of life and raising important questions about security, human rights, and the protection of children. In 2017, the Council of Europe continued to address the aftermath of such events by emphasizing the need for guidelines and frameworks that promote human rights protections in situations involving terrorism and violence against civilians.

By focusing on issues that arose from the Beslan tragedy, the Council of Europe sought to reinforce human rights standards and advocate for better protections against similar acts in the future. This aligns with the organization's core mission to promote human rights, democracy, and the rule of law across its member states.

In contrast, the other options do not accurately reflect a significant event involving the Council of Europe in that year. The UK leaving the EU is more related to EU affairs than the Council of Europe, while the introduction of the European currency and specific human rights guidelines do not directly tie to the 2017 activities or major events associated with the Council of Europe.