answer: Mark compliments Alice's lovely voice and singing. Alice tells him that she learns from a professional teacher.
documents: #Person1#: Alice, I never knew you had such a lovely voice. You really can sing, can't you?
  #Person2#: Thanks, Mark. I used to be a member of the school choir.
  #Person1#: No wonder you can control your voice so well. You are a professional singer.
  #Person2#: Well, you are flattering me. I wouldn't say I am a professional, but I did receive some training at school. My music teacher used to be a professional singer.
  #Person1#: Well, a good teacher makes good students.
  #Person2#: You are quite right.