t->prior->prior=t->next; t->next->prior=t->prior
t->prior->prior=t->prior; t->next->next=t->next
t->prior->next=t->prior; t->next->prior=t->next
t->prior->next=t->next; t->next->prior=t->prior
如图，本题中，把p换成t即可得出正确答案为D。
