Tariff barriers are tbe most common form of trade restriction. A

Tariff barriers are tbe most common form of trade restriction. A tarif is a tax levi commodity when it crosses the boundary of a customs area which usually coincides withof acountry. A customs area extending beyond national boundaries to include two I independent nations is called a customs union.
【正确答案】：关税壁垒是贸易限制最常见的形式。关税是商品跨越关税区边境时,对该商品征收的税。通常关税区同一个国家的领域是一致的。超越国境包括两个或两个以上独立主权国的关税区被称为关税同盟。