Question: What opera company has its permanent home as he Staatsoper Unter den Linden and had Franz Betz as an opera singer in the 1800's?
Context: The Berlin State Opera (German: "Staatsoper Unter den Linden" ) is a German opera company based in Berlin.  Its permanent home is the Staatsoper Unter den Linden, commonly referred to as "Lindenoper", in the central Mitte district, which also hosts the Staatskapelle Berlin orchestra.  Originally the "Hofoper" (court opera) from 1742, it was named "Königliches Opernhaus" (Royal Opera House) in 1844, and "Staatsoper Unter den Linden" in 1918.  From 1949 to 1990 it housed the state opera of East Germany.  Since 2004, the State Opera company belongs to the Berlin Opera Foundation, like the Deutsche Oper Berlin, the Komische Oper Berlin, the Berlin State Ballet, and the Bühnenservice Berlin (Stage and Costume Design). Franz Betz (19 March 1835 – 11 August 1900) was a German bass-baritone opera singer who sang at the Berlin State Opera from 1859 to 1897.  He was particularly known for his performances in operas by Richard Wagner and created the role of Hans Sachs in "Die Meistersinger von Nürnberg". Klaus Häger (born 1965 in Wuppertal) is a German bass singer.  He studied under Franz Müller-Heuser, Ingeborg Most and Jürgen Glauß in Köln and Freiburg, before attending master-classes with Ernst Haefliger and Dietrich Fischer-Dieskau.  From 1991 he was a member of the Hamburg State Opera, and the Staatsoper Unter den Linden in Berlin from 1997.  He is noted in particular for his recordings of J. S. Bach, including BWV 244, 205, 213, 248, 26, 36, 90, 129, 135, 140, 173a, 207, and BWV 243a.  Häger has sung in Lieder recitals and made numerous recordings for German television, and has also performed at festivals such as Salzburg Festival, Schwetzingen Festival, Schleswig-Holstein Musik Festival and Ludwigsburg Festival. The equestrian statue of Frederick the Great is an outdoor sculpture in cast bronze at the east end of Unter den Linden in Berlin, honouring King Frederick II of Prussia.  Designed in 1839 by Christian Daniel Rauch and unveiled in 1851, it influenced other monuments.  After having been enclosed for protection during World War II, the statue and its base were removed by the East Germans in 1950 and re-erected in 1963 at Sanssouci in Potsdam, but returned to Unter den Linden in 1980.  After German reunification the monument was moved back to its original location and restored.  It is a registered monument of the City of Berlin. Leo Blech (21 April 1871 – 25 August 1958) was a German opera composer and conductor who is perhaps most famous for his work at the Königliches Opernhaus (later the Berlin State Opera / Staatsoper Unter den Linden) from 1906 to 1937, and later as the conductor of Berlin's Städtische Oper from 1949 to 1953.  Blech was known for his reliable, clear, and elegant performances, especially of works by Wagner, Verdi, and Bizet's "Carmen" (which he conducted over 600 times), and for his sensitivity as an accompanist. Berlin Brandenburger Tor (in German "Bahnhof Berlin Brandenburger Tor") – formerly Berlin Unter den Linden – is an underground railway station in the central Mitte district of Berlin, Germany, located on the Unter den Linden boulevard near Hotel Adlon, Pariser Platz and Brandenburg Gate.  It is served by the Berlin S-Bahn and U-Bahn, as well as local bus lines. Heinz Fricke (February 11, 1927 – December 7, 2015) was a German conductor.  From 1961 to 1992 he held the position of "Generalmusikdirektor" of the Staatsoper Unter den Linden in Berlin.  He also worked at the Den Norske Opera.  In 2010 Fricke announced his retirement after 18 years with the Washington National Opera and the Kennedy Center Opera House Orchestra (he was appointed to both in 1993).  He was the honorary Music Director Emeritus of the WNO and the KCOHO. What Next?  is the only opera by Elliott Carter.  Paul Griffiths wrote the libretto to the one-act work in 1997/98 on a commission from Staatsoper Unter den Linden in Berlin.  The opera premiered there on 16 September 1999 in a fully staged production conducted by Daniel Barenboim. Bruno Walter (born Bruno Schlesinger, September 15, 1876February 17, 1962) was a German-born conductor, pianist and composer.  Born in Berlin, he left Germany in 1933 to escape the Third Reich, settling finally in the United States in 1939.  He worked closely with Gustav Mahler, whose music he helped to establish in the repertory, held major positions with the Leipzig Gewandhaus Orchestra, New York Philharmonic, Concertgebouw Orchestra, Salzburg Festival, Vienna State Opera, Bavarian State Opera, Staatsoper Unter den Linden and Deutsche Oper Berlin, among others, made recordings of historical and artistic significance, and is widely considered to be one of the great conductors of the 20th century. Kenneth Tarver is an African-American operatic tenor.  He has appeared at some of the world’s most prestigious opera houses, such as the Royal Opera House Covent Garden, Municipal Theatre of Santiago in Chile (as Lindoro in "L'Italiana in Algeri" ), Wiener Staatsoper, Deutsche Oper Berlin, Staatsoper Unter den Linden, Bayerische Staatsoper, Dresden Semperoper, Gran Teatre del Liceu Barcelona, Opéra Comique París, Teatro Lirico Giuseppe Verdi in Trieste, La Monnaie Brussels, Metropolitan Opera, Washington (as Prince Ramiro in "La Cenerentola" ) and Teatro San Carlo Naples.
Answer: Berlin State Opera