大全-349， 关于the more than 500 slaves

1.        In 1791 Robert Carter III, one of the wealthiest plantation owners in Virginia, stunned his family, friends, and neighbors by filing a deed of emancipation, setting free the more than 500 slaves who were legally considered his property.

(A) setting free the more than 500 slaves who were legally considered

(B) setting free more than the 500 slaves legally considered as

(C) and set free more than 500 slaves, who were legally considered as

(D) and set free more than the 500 slaves who were legally considered（A）

(E) and he set free the more than 500 slaves who were legally considered as

答案为A                         deed 【法律】证书，契约

setting... modifys 'a deed' 

But why " the more than 500 salaves"???   the 表示特指么？

有没有可能前文提到过 这500 salaves?

thanks!!!

the slaves, 这些奴隶

the more than 500 slaves， more than 500 插入修饰SLAVES, 指这些超过500（数量）的奴隶

more than the 500 slaves, 比这些（**拥有的500个）奴隶还多的

the 在此是有特指的意思。  对比A C 的不同， 除了setting 与 and set

还有就是  A) 中为  slaves who were legally considered   ////

  who 作限制性定语从句修饰 slaves  ,  既：这些被认为是他的财产的slaves ,   而实际上不是所有的slaves 被认为是他的财产。   因此要加the，  表特指

(C)  slaves, who were legally considered as  

who 作非限制性定语从句修饰 slaves ， 没有A中那个死。

想问一下， C) and set free more than 500 slaves, who were legally considered as

如果 and set 改成 setting 对不对呢，  在此 非限制性定语从句有问题么？？