单选题 I have two grammars, ______ are of great use.
  • A. all of which
  • B. either of which
  • C. both of that
  • D. both of which


【正确答案】 D
【答案解析】主句中的two表明不能选A，从句中的are表明不能选B，both of which用来引导非限制性定语从句。