Final answer:
The nurse is in the implementation phase when selecting interventions for a patient, which is the step where the formulated care plan is executed in the nursing process.
Step-by-step explanation:
When a nurse selects interventions to assist the patient to meet demonstrated needs, the nurse is engaged in the implementation phase of the nursing process. The nursing process is a critical thinking methodology used by nurses to ensure quality patient care and includes five steps: assessment, diagnosis, planning, implementation, and evaluation. During the implementation phase, the nurse puts the care plan into action to meet the goals set during the planning phase.