Are theories of international trade still valid given the new realities of world trade?

Why do nations trade? Why do some people argue that this question may be a bit misleading?
Summarize the three classical theories of international trade.
Compare and contrast the three modern theories of international trade.
What are the major political and economic arguments against free trade?
Are theories of international trade still valid given the new realities of world trade?
How is the concept of opportunity cost related to the theories of absolute advantage and comparative advantage?
Is it possible for all of a country’s resources to be completely mobile? Why or why not?
Devise your own examples that demonstrate your understanding of tariff and nontariff barriers.
What are some of the factors managers might need to consider when assessing the comparative advantage of various locations around the world?
Name and describe the two key components of a balance of trade.