Question: As a child, Olga Peretyatko sand in the children's choir of a theatre that opened in what year?
Sentence (from "Mariinsky Theatre"): Opened in 1860, it became the preeminent music theatre of late 19th century Russia, where many of the stage masterpieces of Tchaikovsky, Mussorgsky, and Rimsky-Korsakov received their premieres.
Relevant evidence: Yes