第28题: [单项选择]The policeman ______ noted something different about the fellow' s accent. A. undoubted B. doubtless C. doubtful D. undoubting 参考答案:B 答案解析:[详细解答] doubtful怀疑的。undoubted和undoubting都有确定的和肯定的之意,其区别为现在分词和过去分词的区别;doubt less既可作形容词,也可以作副词.其它三词只能作形