The most appropriate description of the crime(s) Dallas committed against Reggie in this scenario is c) Bullying. Dallas's actions, including pouring milk on Reggie and insulting him in front of others, constitute bullying behavior. While this incident may also potentially involve charges like assault or harassment, "bullying" specifically captures the nature of the behavior exhibited by Dallas in this context.
Robbery (a) does not apply as there was no theft involved. Domestic Violence (b) is also irrelevant as it pertains to violence in a domestic relationship, which is not the case here. Stalking (d) involves repeated, unwanted attention that causes fear or distress, which doesn't align with the single act described.