[单项选择]单向链表中往往含有一个头结点，该结点不存储数据元素，一般令链表的头指针指向该结点，而该结点指针域的值为第一个元素结点的指针，以下关于单链表头结点的叙述中，错误的是（）。
A. 若在头结点中存入链表长度值，则求链表长度运算的时间复杂度为 O（1）
B. 在链表的任何一个元素前后进行插入和删除操作可用一致的方式进行处理
C. 加入头结点后，代表链表的头指针不因为链表的空而改变
D. 加入头结点后，在链表中进行查找运算的时间复杂度为 O（1）

DOs and DON’Ts
The following DOs and DON’Ts may help you to avoid becoming the victim of a pickpocket.
DO carry with you only what you need; leave in your hotel’s safe such valuables as jewelry, airline tickets, travelers checks, credit cards, extra cash and your passport. Once admitted to France, American tourists do not have to carry passports at all times, a student card or driver’s license usually is enough if you are asked by a police to officer for identification.
DO carry your passport separately from your wallet or handbag. This is not always feasible for women, but men can carry their passports in a front pants pocket or inside jacket pocket.
DON’T have one family or group member carry everyone’s passport; never put a group’s passports in the same bag or briefcase.
DON’T leave your valuables in a locked car, locks are easily opened by experts, the trunk is not safe either.
DOs