John is an instructor in a college in the Mid-Atlantic region of the United States where he teaches several courses in management. In most of his courses, he had students work in groups to write term projects. He has observed that students often go through several phases of their group projects. For example, he has specifically observed that the groups go through transitions between inertia and activityat the halfway point, they experience an increase in productivity. Which model better explains what John has observed? a. Group stage model. b. Punctuated equilibrium model. c. Team effectiveness model. d. Congruence model