The efficiency case made for free trade is that as trade distortions such as tariffs are dismantled and removed ___________.
选项：

A:government tariff revenue will decrease, and therefore national economic welfare will decrease.;
B:government tariff revenue will decrease, and therefore national economic welfare will increase.;
C:deadweight losses for producers and consumers will decrease, hence increasing national economic welfare.;
D:deadweight losses for producers and consumers will decrease, hence decreasing national economic welfare.