Which of the following three municipalities make up the Research Triangle of North Carolina?

The Research Triangle, commonly referred to as simply "The Triangle", is a region in the Piedmont of North Carolina in the United States, anchored by North Carolina State University, Duke University, University of North Carolina at Chapel Hill, and the cities of Raleigh and Durham and the town of Chapel Hill. The "Triangle" name was cemented in the public consciousness in the 1950s with the creation of Research Triangle Park, home to numerous high-tech companies and enterprises. Although the name is now used to refer to the geographic region, "the Triangle" originally referred to the universities, whose research facilities, and the educated workforce they provide, have historically served as a major attraction for businesses located in the region.