第18题: [单项选择]The barriers to trade may take any form including import duties,import licenses,export licenses,import quotas,tariffs,subsidies and( )to trade. A. export system B. international trade policy C. import system D. non-tariff barrier 参考答案:D 答案解析:[解析] 贸易壁垒主要是指一国对外国商品或劳务进口所实行的各种限制措施,一般分为关税壁垒和非关税壁垒(non-tariff barrier)两类。