A. p->next=s ; s->prior=p; p->next->prior=s ; s->next=p->next

B. p->next->prior=s; p->next=s; s->prior=p; s->next=p->next

C. s->prior=p; s->next=p->next; p->next=s; p->next->prior=s

D. s->next=p->next; p->next->prior=s ; s->prior=p; p->next=s