职业道德规范可以（）从业人员和服务对象之间的关系。
A.改正
B.建立
C.调节
D.学习
参考答案：B
I didn't see Laura at the party last night. Do you know _______? [ ]
A. why didn't she come
B. what happened
C. when would she arrive
D. where she has been
带头结点的单链表first为空的判定条件是（）。
A.first==NULL
B.first->1ink==NULL
C.first->link==first
D.first!＝NULL
