单项选择题

A.p→next=s; p→next→prior=s; S→prior=p; S→next=p→next;
B.s→next=p; s→next=p→next; p→next=s; p→next→prior=s;
C.p→next=s; s→prior=p; p→next→prior=s; s→next=p→next;
D.s→prior=p; s→next=p→next; p→next→prior=s; p→next=S;