He told us how he dealt with the self-interest of countries to bring them into a kind of international accord ________everyone seemed to benefit.
句意：他告诉我们他是如何处理各国之间的利益关系的，即让各国达成一种令彼此均受益的国际协定。where引导定语从句，修饰前面的抽象名词accord。故正确答案为A。