Explanation: When a client is experiencing an anaphylactic reaction, ensuring airway patency is the nurse's first priority. Airway obstruction due to swelling or bronchospasm can rapidly lead to respiratory distress and hypoxia. Assessing airway patency allows the nurse to determine the severity of the situation and initiate appropriate interventions.

A) Administering epinephrine

Epinephrine is a critical medication for treating anaphylaxis, but the nurse must first ensure airway patency before administering any medication. The administration of epinephrine would follow the assessment and confirmation of airway patency.

B) Calling for emergency assistance

While calling for emergency assistance is essential in managing anaphylactic reactions, it should not take precedence over assessing airway patency. The nurse must first assess the client's immediate condition and initiate interventions to secure the airway.

D) Positioning the client in a supine position

Positioning the client in a supine position may be appropriate in some situations, but it is not the first priority when managing an anaphylactic reaction. Airway assessment and intervention should be the initial focus to address potential airway obstruction.

A nurse is providing education to a client about self-management of allergic reactions.