Detailed Instructions: In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Problem:Question: When did the opera house where  Elsa Cavelti sang leading dramatic contralto in 1944 open? Passage:In 1944, she returned to Switzerland, singing as the leading dramatic contralto at the Opernhaus Zürich. She appeared as Brangäne in Wagner's Tristan und Isolde, as Fricka in his Die Walküre, as Ortrud in his Lohengrin, and in the title role (Octavian) of Der Rosenkavalier by Richard Strauss, among others. In 1949, she took part in the premiere of Willy Burkhard's Die schwarze Spinne. The same year, she performed in Monteverdi's L'incoronazione di Poppea, both at Vicenza's Teatro Olimpico and at La Fenice in Venice. She performed as a guest at La Scala in Milan several times, including Octavian, Brangäne, Venus in Wagner's Tannhäuser, and the title role of Honegger's Judith. She appeared as a guest at the Vienna State Opera, in Belgium, France, United Kingdom, in Argentina, and the US.
 Links: a. Teatro Olimpico b. Zürich Opera House c. Zürich Opera House d. Lohengrin (opera)
Solution:
b