Final answer:
When a nurse is preparing medication for a client and is called away to an emergency, the nurse should lock the medications in a cart and finish them upon return to ensure safety and security.
Step-by-step explanation:
In this scenario, when a nurse is preparing medication for a client and is called away to an emergency, the nurse should lock the medications in a cart and finish them upon return. This is to ensure the safety and security of the medications, as well as to prevent any contamination or errors in administration.
Having another nurse finish preparing and administering the medications (option b) may not be ideal as it introduces a break in continuity of care. Putting the medications back in the containers (option a) may also pose risks of contamination or errors.
Having another nurse guard the preparations (option d) may not be the most efficient use of staff resources, especially in an emergency situation.