Which of the following defines a complex high power rocket?

A complex high power rocket is typically defined by its configuration and the complexity of its design. The correct choice indicates that such a rocket can be multi-staged or propelled by more than one motor, which directly contributes to its complexity. Multi-staging allows for a more efficient ascent by jettisoning parts of the rocket that are no longer needed as it climbs, and using multiple motors can provide additional thrust or redundancy in propulsion systems.

While other options may describe certain regulations or requirements surrounding high power rocketry, they do not inherently define the complexity of the rocket itself. For instance, simply being restricted to a specific motor class doesn't describe the rocket's structure or operational intricacies. Similarly, the requirement for special training to launch and the stipulations about designated launching sites relate to the safety and regulatory aspects of launching such rockets, rather than their inherent complexity. These aspects ensure safe operation and compliance with guidelines but do not capture what makes a rocket complex in terms of its design and functionality.