单选题 Mr. Thompson was very uncertain ______ whether it was the right decision in teaming up with his coworker, Mr. Barns.
  • A. for
  • B. if
  • C. as to
  • D. even though
【正确答案】 C
【答案解析】[解析] 语法：介词 1．选项由介词和连词构成。 2．空格后已有连词whether引导名词性从句，因此连词B选项和D选项排除。 3．as to和介词about意义相同。与句意相符，因此C为正确选项。