There must be at least 1 nursing staff on duty per ____ residents.

The correct answer indicates that there must be at least one nursing staff member on duty for every 20 residents in a healthcare facility. This ratio is crucial to ensure that residents receive adequate supervision and care, especially in settings such as nursing homes or long-term care facilities, where the needs of residents can vary significantly and may require prompt attention from nursing staff.

Having one nursing staff member for every 20 residents enables better monitoring of health conditions, timely response to emergencies, and more personalized attention for each resident. This standard helps maintain a safe and supportive environment, which is essential for the well-being of the residents.

The choice reflects established guidelines or regulations in healthcare environments that highlight the importance of proper staffing ratios to ensure quality of care. Other ratios mentioned in the incorrect options may not meet the necessary demands for sufficiently supporting the residents' health and safety.