中文摘要：

令G为有限群,S为G的非空有限子集,G关于S的双凯莱图BC（G,S）是一个二部图,其顶点集是G×{0,1},边集是{（g,0）（sg,1）｜g∈G,s∈S}.若有完美匹配的连通图Γ至少有2n＋2个顶点,且每一个大小为n的匹配都可以扩充为一个完美匹配,则称此完美匹配的连通图Γ是n-可扩的,并对二面体群的双凯莱的2-可扩性进行了刻画.

英文摘要：

Let Gbe a finite group and Sa nonempty subset（possibly containing the identity element）of G.The biCayley graph BC（G,S）of G with respect to Sis defined as the bipartite graph with vertex set G×{0,1}and edge set{（g,0）（sg,1）｜g∈G,s∈S}.A connected graphΓadmitting aperfect matching is called n-extendable wheneverΓhas at least 2n＋2vertices,and every matching of size ncan be extended to a perfect matching ofΓ.The 2-extendable bi-Cayley graphs of dihedral groups are characterized.