答案及解析：[单选题]A graph with an (undirected) edge between any two vertices is called a complete graph, and a complet

问题：

[单选题]

A graph with an (undirected) edge between any two vertices is called a complete graph, and a complete graph containing n vertices is represented by Kn Which of the following figures must not be a plan? 任何两个顶点间都有一条（无向）边的图称为完全图，包含n个顶点的完全图用Kn表示。下列哪个图一定不是平面图？