What is the fundamental principle behind the 'graduated' aspect of a GDL program as a driver advances through its stages?

1. To require drivers to demonstrate proficiency on different classes of vehicles at each stage.
2. To allow drivers to gradually gain experience in lower-risk situations before being exposed to more complex driving conditions.
3. To ensure all new drivers pay a series of escalating fees for each license stage.
4. To provide law enforcement with more opportunities to issue citations to new drivers.