challenge: Who were some of the notable instructors Heinrich Dorn studied with in Berlin?
  
  A. Ludwig Berger, Bernhard Klein, and Carl Friedrich Zelter
  B. Johannes Brahms, Franz Liszt, and Richard Wagner
  C. Ludwig van Beethoven, Franz Schubert, and Robert Schumann
  D. Felix Mendelssohn, Giacomo Meyerbeer, and Otto Nicolai
  Answer: 