Quotas or quantitative restrictions are the most common form of

Quotas or quantitative restrictions are the most common form of non-tariffbarriers. A quota limits the imports or exports of a commodity during a givenperiod of time. The limits may be in quantity or value terms, and quotas may beon a country basis or global，without reference to countries.
【正确答案】：配额或数量限制是非关税壁垒最常见的一种形式。配额在一定时期内限制一种商品的进出口。其限制可以以数量计算，也可以以价值计算，配额可以是针对国家的或者是全球性的，而不针对特定国家。
【题目解析】：参见教材P90。