OG 11 51请教

51. 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

请问这里in that 为什么说使用的stilted and over formal？XDF不说in that 是正确答案的标志么？谢谢帮忙了~！

同学你好: 首先, festival's month就是错误的.因为这不是有生命的,所以不能用's.  排除A B

谢谢楼上的讲解，但是我想问的是in that 的用法，为什么这里有stilted and over formal这样的错误存在？不是说in that 是最标准的商业用法么？