The correct option is E a treatise that argued for equal political and legal rights for women
There are three errors in the given sentence. The first error is the use of 'a treatise' because we want to refer to "Discourse on Women" (its the name of a particular article). So, instead of 'a', we should use 'the treatise'.Also, it is quite clear from the sentence that the 'arguing' will be done in "Discourse on Women", so, the use of 'the treatise' is not needed. Secondly, though 'arguing' modifies the previous clause ( comma + verb-ing preceded by a clause modifies the said clause) it does not add anything to the clause that talks about the 'publishing' of the treatise. Finally, the sentence requires a parallelism that it's missing- 'for women to have equal political and legal rights' and 'for changes in the married women's property laws' should be parallel to each other. The appropriate parallel structure would be "for equal political and legal rights for women" AND "for changes in the married women's property laws". Options A and B contain these errors and are incorrect. Option C contain a non-idiomatic structure in the non-underlined part- 'for the changes in ...' is inappropriate with 'advocates' because 'advocates ... for' is incorrect. In D, the use of 'advocating' is inappropriate with regard to the non-underlined part of the sentence. Thus, E is the correct choice as it avoids all these errors.