Final answer:
The seller should refuse to sell the age-restricted product to Mr. Oswald since he is known to be purchasing it for a minor, which is against the law.
Step-by-step explanation:
If Mr. Oswald's ID shows he is of legal age and is purchasing an age-restricted product for a minor, it falls under the responsibility of the seller to adhere to the laws regarding such sales. The correct action would be to refuse to sell the product to Mr. Oswald. Selling age-restricted products to an adult who is known to be purchasing for minors is against the law. In this scenario, it is known that Mr. Oswald is purchasing the product for a minor, therefore, it would be correct to refuse the sale to prevent any illegal distribution of age-restricted items to minors.