单选题 Great as Newton was, many of his ideas ______ today and are being modified by the work of scientists of our time.
  • [A] are to challenge
  • [B] may be challenged
  • [C] have been challenged
  • [D] are challenging


【正确答案】 C
【答案解析】[解析] 根据句意，所填空应使用被动语态，因此首先排除[A]和[D]。[B]may be challenged和后半句中的are being modified相矛盾，故答案为[C]。