在中向p所指的结点之前插入一个结点q的操作为( )
A.
p->prior=q;q->next=p;p->prior->next=q;q->prior=p->prior;
B.
q->prior=p->prior;p->prior->next=q;q->next=p;p->prior=q->next;
C.
q->next=p;p->next=q;q->prior->next=q;q->next=p;
D.
p->prior->next=q; q->next=p; q->prior=p->prior;p->prior=q;