A homeless male who was found sitting in the middle of a busy street is brought to the emergency department (ED). On admission, the client is confused and has difficulty answering questions. After ruling out a physiological etiology for the client's behavior, he is transferred to the mental health unit. When admitting the client to the unit, which action is most important for the nurse to take?

B Perform a mental status exam. C Assess the client from head-to-toe. A Ask the client about his recent substance use. D Determine the number of previous hospitalizations.