Amswer is E

(A) Salmon is the chief export of Country B, accounting for a substantial proportion of its export earnings over each of the last three years. - Not relevant

(B) The supply of native salmon has become increasingly limited in certain parts of North America in the past decade, including many parts of the United States. - Not relevant

(C) Salmon from Country B is considered a delicacy in all of the European nations that imported salmon last year. - Strengthens the economist's view

(D) The economic value to U.S. companies of the adoption of intellectual property regulations in Country B is greater than the value of salmon exports from Country B. - In this case, Country B would not mind circumventing the ban

(E) Costs for the transportation of salmon from Country B to Europe would make salmon from Country B more expensive for European consumers than salmon imported from other countries. - In other words, European consumers may not import salmon from Country B all that much.

Hence, the answer is E.