答案:The import quota is in contrast to the tariff, which specifies an amount or percentage of tax but then lets the market determine the quantity to be imported with the tariff in existence. Quotas are more certain and precise as trade restraint than are tariffs. An import duty that is not prohibitive will reduce imports, but it does not impose an absolute limit on imported goods. A quota system limits with certainty the extent of foreign competition in the domestic market. A quota differs from a tariff in that the quantity of imports is fixed and domestic price adjusts, whereas with a tariff, the domestic price is altered and quantity adjusts.