A.
p->next->prev = p->prev; p->prev->next = p->prev; delete p;
B.
p->next->prev = p->next; p->prev->next = p->next; delete p;
C.
p->next->prev = p->next; p->prev->next = p->prev; delete p;
D.
p->next->prev = p->prev; p->prev->next = p->next; delete p;