Final answer:
The social worker should first help the client identify alternative social supports after discharge.
Step-by-step explanation:
The first step the social worker should take in this situation is to help the client identify alternative social supports for after discharge (C).
Since the client's parents have expressed their intention to never speak to their son again, it is important for the social worker to assist the client in finding other sources of support and connection. This can include helping the client build relationships with other family members, friends, or support groups.
Once the client has identified alternative social supports, the social worker can then work with the client to develop a treatment plan (B) that takes into account their specific needs and goals.