---OG---重大错误----已解决，谢------>>>Zeros大牛！！！

12.    The Olympic Games helped to keep peace among the pugnacious states of the Greek world in that a sacred truce was proclaimed during the festival’s month.
(A) world in that a sacred truce was proclaimed during the festival’s month
(B) world, proclaiming a sacred truce during the festival’s month
(C) world when they proclaimed a sacred truce for the festival month
(D) world, for a sacred truce was proclaimed during the month of the festival
(E) world by proclamation of a sacred truce that was for the month of the festival

the key is C. but "they" 前面有两个复数Olympic Games and pugnacious states。

should be D.