Countries Restrict International Trade for All of the Following Reasons

Countries restrict international trade for all of the following reasons except:

A) international trade probably will lead to the displacement of workers.
B) the benefits of trade usually are limited to small groups, whereas the costs are widely scattered across the population.
C) it is sometimes difficult to decide where a country's comparative advantage lies when "learning by doing" effects are important.
D) economies of scale can mean that a country is able to develop a comparative advantage by protecting infant industries.