Concept:A physical import restriction directly limits the quantity of goods entering a country.Explanation:A ban completely stops the importation of a product, so it does not merely restrict the quantity.Excise duty and import tax are monetary charges placed on goods; they make imports costlier but do not physically cap the amount.A quota is a government-imposed limit that sets the maximum quantity of a particular product that may be imported within a given period.Since the question asks for a physical restriction on the quantity of imported goods, the correct answer is a quota.Answer:B. A quota