GMAT Critical Reasoning (CR) | Re: An obscure novel from the thirteenth century has been attributed to

I believe that the argument speaks about chronology and not the authorship. It explicitly states that there is doubt regarding authorship but chronology is clear. Hence, we should find an option proving that the work was completed in 1221 and not one which is trying to prove that the author is indeed X.

Only 'C' is adding more info onto this. It says no other author has mentioned about this work after 1221, hence the novel was completed in 1221.

All the other options throw more light onto the
...

---