The correct answer is B.
An import quota is used by protectionist policymakers to establish a quantitative restriction on the amount that can be imported of a certain product and/or from a certain country or trade area.
Therefore, a quota is expressed in kilograms (621,780 kg) and not as a percentage of the total value of the goods imported (option A)as in the case of tariffs, not as a price to be paid in exchange for a certain quantity of goods (option C) or also not as a percentage of the total profits that will be made with the imported goods.