Final answer:
The primary difference between boundary crossing and a boundary violation is C) The severity of consequences. The primary difference between boundary crossing and a boundary violation is the severity of the consequences, with violations typically causing harm or exploitation.
Step-by-step explanation:
The primary difference between boundary crossing and a boundary violation is C) The severity of consequences. A boundary crossing may not necessarily have severe consequences and can sometimes be therapeutic in the context of professional relationships. In contrast, a boundary violation is a serious breach of professional roles that typically results in harm or exploitation. An example of a boundary crossing could simply entail a therapist disclosing personal information to build rapport, whereas a boundary violation might involve a relationship with a client that is romantic or sexual in nature, which is both unethical and harmful.