双链表的每个结点包括两个指针域。其中rlink指向结点的后继,llink指向结点的前驱。如果要
A)p↑.rlink↑.llink:=q;p↑.rlink:=q;q↑.llink:=p;q↑.rlink:=p↑.rlink;
B)p↑.llink↑.rlink:=q;p↑.llink:=q;q↑.rlink:=p;q↑.llink:=p↑.llink;
C)q↑.llink:=p;q↑.rlink:=p↑.rlink;p↑.rlink↑.llink:=q;p↑.rlink:=q;
D)q↑.rlink:=p;q↑.1link:=p↑.llink;p↑.1link↑.rlink:=q;p↑.llink:=q;