Final answer:
The priority nursing action should be to provide age-appropriate activities.
Step-by-step explanation:
The priority nursing action that should be included in the plan of care for a 16-year-old patient with Down Syndrome and a mental age of 5 in the Acute Care hospital is to provide age-appropriate activities.
Children with Down Syndrome typically have developmental delays and intellectual disabilities. By providing age-appropriate activities, the nurse can promote the patient's cognitive, physical, and social development, helping them reach their full potential.
For example, the nurse can engage the patient in activities such as puzzles, board games, art and crafts, and storytelling, which are suitable for their mental age and can help improve their skills in various areas.