第11题: [单项选择]在有向图G的拓扑序列中,若顶点Vi在顶点Vj之前,则下列情形不可能出现的是( )。 A. G中有弧<Vi,Vj> B. G中有一条从Vi到Vj的路径 C. G中没有弧<Vi,Vj> D. G中有一条从Vj到Vi的路径 参考答案:D 答案解析:[解析] 选项A、B、C都是有可能出现的,但是选项D是不可能出现的,因为若是G中有一条从Vj到Vi的路径,则在图的拓扑序列中顶点Vj应
第18题: [单项选择]A. Sue looks older in the picture than she really is. B. Sue should wear makeup when taking photos. C. Sue is the oldest among the people in the picture. D. Sue should remove this picture from her photo album. 参考答案:A 答案解析:[听力原文] W: That picture certainly flatters Sue. She looks great in the picture. Don’t you think so