Final answer:
The best way to satisfy the customer when the item is out of stock is to apologize and explain that more stock will be available next week.
Step-by-step explanation:
The best way to satisfy the customer when the item is out of stock is option C: apologize to the customer and explain that you will have more in stock next week. Apologizing shows the customer that you acknowledge their concern and value their business. Additionally, informing them that more stock will be available next week provides a solution and maintains their trust in your store. Offering a substitution with two 50-count bottles, as option D suggests, may not be the ideal solution as it may not meet the customer's needs or preferences.