Why where there are no differences among countries in the basic

Why where there are no differences among countries in the basic capabilities at producing goods, other bases for trade among them may still exist?
【正确答案】：First, patterns of demand may differ among nations. Second, trade may occur out of economies of scale，that is，the cost advantages of large-scaleproduction.Third, trade takes place because of innovation or style.
【题目解析】：参见教材P81。