Final answer:
The factor in how much tariff a firm must pay when importing a product is from which country the product was imported. Therefore, the most appropriate option is D.
Step-by-step explanation:
The factor in how much tariff a firm must pay when importing a product, such as men's pants, is d. From which country the product was imported. Tariffs are taxes imposed on imported goods by governments, and the amount of tariff a firm has to pay depends on the country from which the product is imported. Different countries may have different tariff rates or exemptions for certain goods.