Prime Minister Justin Trudeau takes part in a question-and-answer session at the Council on Foreign Relations in New York on April 28.Sean Kilpatrick/The Canadian Press Prime Minister Justin Trudeau on Friday suggested that China uses slave labour in the production of lithium as he discussed Canada’s efforts to ramp up production of the critical metal used in electric vehicle and other batteries. Canada last fall announced a tougher policy on critical mineral investment - particularly from dominant producer China - as it worked to shore up its domestic supply of critical minerals after the global pandemic exposed supply chain problems...