Question: The composer Alexander Borodin, who wrote the opera Prince Igor, was a part of which group dedicated to producing a uniquely Russian kind of classical music? 
Sentence (from "Prince Igor"): The composer adapted the libretto from the Ancient Russian epic "The Lay of Igor's Host", which recounts the campaign of Rus' prince Igor Svyatoslavich against the invading Cuman ("Polovtsian") tribes in 1185.
Relevant evidence: No