Final answer:
In Phase II, simulations serve as the primary source of training, offering an interactive environment for students to apply learned concepts and engage in realistic scenarios.
Step-by-step explanation:
The main source of training in Phase II is simulations. Simulations provide a realistic and immersive environment for students to apply the concepts they have learned. In educational settings, such as physics, students are often directed to use simulations like the interactive PhET physics simulations developed by the University of Colorado Boulder to deepen their understanding of the subject matter.