Even in a Situation Where Absolute Costs for Two Countries

Even in a situation where absolute costs for two countries and two products are identical, trade can be mutually beneficial if:

A) tastes differ substantially between the two countries.
B) economies of scale in the production of both products encourages specialization.
C) a third product is introduced and paired with one of the former products.
D) answers a.and b.
E) none of the above.