第11题: [单项选择]Great as Russell was, many of his ideas ______ today and are being modified by the work of philosophers of our time. A. are to challenge B. may be challenged C. have been challenged D. are challenging 参考答案:C 答案解析:时态题。根据逻辑关系首先可以确定应该为被动结构,排除选项[A]、[D],又因为这一行为一直延续到现在,所以用现在完成时。正确答案为[C]。