A Trade-Diverting Customs Union Is More Likely to Lead to Trade

A trade-diverting customs union is more likely to lead to trade creation:

A) the lower are the pre-union trade barriers of the member countries
B) the lower are the customs union's barriers on trade with the rest of the world
C) the smaller is the number of countries forming the customs union and the smaller their size
D) the more complementary rather than competitive are the economies of the nations forming the customs union