Final answer:
The priority for a nurse when a child is experiencing an anaphylactic reaction is to administer epinephrine immediately due to its life-saving ability to improve breathing, increase blood pressure, and reduce airway swelling.
Step-by-step explanation:
The priority action by a nurse caring for a school-age child experiencing an anaphylactic reaction is to administer epinephrine. Anaphylaxis is a life-threatening allergic reaction characterized by symptoms such as respiratory distress, drop in blood pressure, and swelling of the tongue and throat that can lead to suffocation. The immediate administration of epinephrine is crucial since it works to constrict blood vessels to increase blood pressure, relax bronchial muscles to improve breathing, and reduce swelling that may block airways. Therefore, the correct answer to the question is a) Administering epinephrine.