Choice "A" is correct. A seller who sells goods on credit and retains a security interest in the goods to secure the purchase price has a purchase money security interest (PMSI). A PMSI in consumer goods is automatically perfected; there is no need to file.
Choices "d", "b", and "c" are incorrect. If Mars sells to retailers or wholesalers, the collateral is inventory, since it is held by the debtor for sale to others. A security interest in inventory is not automatically perfected, even if the secured party has a purchase money security interest. The fact that a wholesaler sells to buyers in the ordinary course addresses the question of whether the buyers will be subject to Mars' security interest and does not affect Mars' need to file.