Final answer:
In the scenario presented, the immediate action mandated by law for the nurse is to contact the appropriate community child protection agency to ensure the safety of the unsupervised children.
Step-by-step explanation:
If a nurse notices that a neighbor's preschool children are repeatedly playing on the sidewalk and in the street unsupervised, and the situation persists despite communication with the parents, the immediate action mandated by law is b. Contact the appropriate community child protection agency. This action ensures the safety of the children and follows the legal requirement to report suspected neglect or endangerment to authorities. Many professionals, including those in healthcare and education, are required to report such incidents under mandatory reporting laws to protect vulnerable individuals like children from potential harm.
Infants and young children are particularly susceptible to neglect due to their total dependence on their caregivers for survival. When parents fail to provide adequate supervision and safety, despite having access to public or private services that can help, intervention by child welfare services is necessary and justified. It's essential to prevent further risk and the possibility of tragic outcomes, similar to those described in the counter-example situation involving a babysitter and unattended children with hazardous materials.