单项选择题

A.p->prior=q;q->next=p;p->prior->next=q;q->prior=p->prior;
B.p->prior->next=q;q->next=p;q->prior=p->prior;p->prior=q;
C.q->prior=p->prior;p->prior->next=q;q->next=p;p->prior=q->next;
D.q->next=p;p->next=q;q->prior->next=q;q->next=p;