OG153和倒装结构

153. A recording system was so secretly installed and operated in the Kennedy Oval Office that even Theodore C. Sorensen, the White House counsel, did not know it existed.

(A)  A recording system was so secretly installed and operated in the Kennedy Oval Office that

(B)   Installed and operated so secretly in the Kennedy Oval Office was a recording system that

排除后剩下这两个选项，答案是A,但B除了用倒装结构外也没问题啊。

顺便请大家帮帮忙，一起总结一下倒装结构的用法（论坛里关于这一用法的讨论不多，但前段时间考G的同学都反应考试中涉及这一考点的很多）。

参阅

http://forum.chasedream.com/dispbbs.asp?BoardID=23&ID=24461