What Is One Reason International Specialization Would NOT Occur

What is one reason international specialization would NOT occur?  

A)  because some countries have educated, trained workers, while other countries have unskilled workers 
B)  because tastes and preferences tend to be different in different countries 
C)  because economies of scale can allow larger producers to operate at lower average cost 
D)  because the world price of a good is determined by the world supply and demand for it