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。如果要在p所指结点前面插入q所指的新结点，下面哪一个操作序列是正确的______。

A．p ↑.rlink ↑.1link:=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 ↑.llink:=p ↑.llink;p ↑.llink ↑.rlink:=q;p ↑.llink:=q;