Dallas committed b. Bullying against Reggie. The act of pouring milk on Reggie and verbally abusing him constitutes bullying behavior, especially given the context of ongoing harassment and derogatory treatment he has faced from other students. This behavior includes humiliation and intimidation, which are key components of bullying.
If considering legal frameworks, other possible charges could include assault, depending on the jurisdiction and specific laws regarding harassment, but bullying is the most direct label for the behavior as described.