Final answer:
To test the product and ensure it is in proper working condition, you should check if it is defective.
Step-by-step explanation:
To test the product and ensure it is in proper working condition, you should check if it is defective. A defective product refers to one that has a fault or flaw that prevents it from functioning correctly. Other options like being damaged free, expired, or out of stock do not directly relate to the functionality of the product.