16. Mom bought me ______ MP3 for my birthday present last Sunday.
  A. the      B. an      C. a       D. 不填
17. ---How long have you _______?
---5 years.
  A. married    B. got married    C. married    D. been married
18. The singer became famous in the early 1980s, ______ the classical music was better than pop music.
  A. which        B. when      C. that     D. where