What does the term “Triad” refer to? What is meant by Quad?

What does the term “Triad” refer to? What is meant by Quad?
【正确答案】：The term Triad refers to the three richest regions of the world the United States, the European Union and Japan that offer the most important business opportunities.Some people extend the scope of Triad to include Canada and name the broadened grouping Quad.