Canadian Prime Minister Justin Trudeau attends the plenary session during the World Economic Forum (WEF) annual meeting at Congress Center in Davos, Switzerland, Jan. 23, 2018. Heads of state called for 2018 to be the year of collaboration and multilateralism to address major global challenges like climate change, terrorism and protectionism, as the World Economic Forum opened in Davos, Switzerland, on Tuesday. (Xinhua/Xu Jinquan)