EX15Q11:到底应不应该有？

HardyNiborUID: 3461489

And it is true that the publicly acknowledged leaders of an uprising frequently write memoirs. However, such documents are likely to be highly unreliable, unrepresentative, and unsystematically preserved, especially when compared to the detailed judicial dossiers prepared for everyone arrested following a failed insurrection. As a consequence, it may prove difficult or impossible to establish for a successful revolution a comprehensive and trustworthy picture of those who participated, or to answer even the most basic questions one might pose concerning the social origins of the insurgents.


Which of the following can be inferred about the
"detailed judicial dossiers" referred to in line 50?
答案是
Information contained in the dossiers sheds
light on the social origins of a revolution's
participants.

加黑的部分说后面的事很难。什么情况下呢？如果理解成simply by memoir的话是对的，可是拿来对比的dossier不是已经存在了的么？那么就应该理解成有了dossier之后，了解参与者的社会身份仍然是困难的。这就把这个选项排除掉了。

怎么搞的，各位看看