认真看了些 很复杂 有不同的奶制品不同的价格制度

有问题的只是一种，其它的是没有关税的

"Canadian officials have been told that they are not allowed to subject American diafiltered milk imports to what’s known as a tariff rate quota (TRQ) – that cap the amount of product allowed in. That’s meant the American dairy industry has had complete and unfettered access to the Canadian market place for diafiltered milk for several years. (Diafiltered milk is not used by American dairy processors.)"