在带尾指针 clist 的循环单链表中（结点数 $\ge 3$），下面操作描述正确的是（ ）。

{{ select(1) }}

• 头部插入：p -> next = clist -> next -> next; clist -> next = p;
• 尾部插入：p -> next = clist -> next; clist -> next = p; clist = p;
• 头部删除：p = clist -> next; clist -> next = p -> next -> next; delete p;
• 尾部删除：p = clist; clist = clist -> next; delete p;