Final answer:
The nurse should notify the security staff to conduct a room search while staying with the client.
Step-by-step explanation:
The nurse should take action C) Notify the security staff to conduct a room search while staying with the client. It is important for the nurse to take the client's concerns seriously and ensure their safety. However, removing the client from the room and searching for the alleged bomb may escalate the client's anxiety and reinforce their delusions. Telling the client that there's no bomb may invalidate their experience and cause further distress.