指针p、q和r依次指向某循环链表中三个相邻的结点，交换结点*q和结点*r在表中次序的程序段是 ( )

A．p—＞next=r; q—＞next=r—＞next; r—＞next=q;
B．p—＞next=r; r—＞next=q; q—＞next=r—＞next;
C．r—＞next=q; q—＞next=r—＞next; p—＞next=r;
D．r—＞next=q; p—＞next=r; q—＞next=r—＞next;