Anyone trying to be my friend or talk?

Which statement is true with regard to beethoven? a. ludwig vin kochel catalogued more than six hundred of his compositions. b. he was the official composer for the powerful and rich eszterhazy family. c. he produced the best piano sonatas and the “ninth symphony” after losing his hearing. d. he wrote the well-known opera “the magic flute” during the last years of his life.