Final answer:
The nurse's first action should be to assess Maria's needs and comfort to determine the cause of her crying, which might include pain or other factors.
Step-by-step explanation:
The first action a nurse should take when notified that a patient, named Maria in this scenario, is crying and may be in pain is B. Assess Maria's basic needs and comfort. It is essential to perform a thorough assessment to determine whether her crying is indeed due to pain or if there are other factors at play, such as emotional distress or a different medical issue. This assessment allows the nurse to provide appropriate and individualized care, which may include administering pain medication if that's part of Maria's care plan and after ensuring it's safe and necessary based on the assessment findings.