What terms must you use instead of "free" in advertising when the customer must purchase something to receive the "free" merchandise?

Answer: C — "included with"

Using the term "additional charge" would be incorrect because the purchase is required in order to receive the free merchandise. "At no extra cost" also implies that the free merchandise is included without any additional payment, which is not the case when the customer must purchase something. "No purchase necessary" is also incorrect because it would imply that the customer can receive the free merchandise without making a purchase, which is not what the question is asking. Therefore, the most appropriate term to use in this scenario is "included with." This indicates that the free merchandise is bundled or included with the purchase, without implying that it is completely free of cost.