题目：在双向链表指针p的结点之前插入一个指针q的结点操作是（ ）。
A. p->prior =q;q->next=p;p->prior->next=q;q->prior=q;
B. p->prior =q;p->prior->next=q;q->next=p;q->prior=p->prior;
C. q->next =p;q->prior=p->prior;p->prior->next=q;p->prior=q;
D. q->prior =p->prior;q->next=q;p->prior=q;p->prior=q;
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