Question: Sextet was by the Polish composer who has completed how many operas?
Sentence (from "Krzysztof Penderecki"): Among his best known works are his "Threnody to the Victims of Hiroshima", "Symphony No. 3", "St. Luke Passion", "Polish Requiem", "Anaklasis", "Utrenja", four operas, eight symphonies and other orchestral pieces, a variety of instrumental concertos, choral settings of mainly religious texts, as well as chamber and instrumental works.
Relevant evidence: Yes