单选题 (There) is an unresolved controversy as to (whom) (is) the real author of the Elizabethan plays (commonly) credited to William Shakespeare.
  • A. There
  • B. whom
  • C. is
  • D. commonly


【正确答案】 B
【答案解析】将whom改为who。这是介词短语as to的宾语从句，关连词who是从句的主语，故不能用who的宾格形式。