在研究紊流边界层的阻力特征时，所谓粗糙区是指粘性底层的实际厚度Δ小于粗糙高度。

( )是一项分化、瓦解和改造犯罪分子的有效刑事政策。

A．严肃与谨慎相结合的政策

B．惩办与宽大相结合的政策

C．依法从重从快惩处严重刑事犯罪分子的政策

D．重证据，重调查研究，严禁逼供信的政策

世界地图:地球仪

A．一元纸币:一元硬币

B．纸飞机:飞机模型

C．肖邦画像:肖邦雕塑

D．楼房平面图:楼房三维图

Parents should stop blaming themselves because there's not a lot they can do about it. I mean the teenager problem. Whatever you do or however you choose to deal with it, at certain times a wonderful, reasonable and helpful child will turn into a terrible animal.

I've seen friends deal with it in all kinds of different ways. One strict mother insisted that her son, right from a child, should stand up whenever anyone entered the room, open doors and shake hands like a gentleman. I saw him last week when I called round. Sprawling himself on the sofa in full length, he made no attempt to turn off the loud TV he was watching as I walked in, and his greeting was no more than a quick glance at me. His mother was ashamed. "I don't know what to do with him these days," she said. "He's forgotten all the manners we taught him."

He hasn't forgotten them. He' s just decided that he' s not going to use them. She confessed that she would like to come up behind him and throw him down from the sofa onto the floor.

Another good friend of mine let her two daughters climb all over the furniture, reach across the table, stare at me and say, "I don't like your dress; it's ugly." One of the daughters has recently been driven out of school. The other has left home.

"Where did we go wrong?" her parents are now very sad. Probably nowhere much. At least, no more than the rest of that unfortunate race, parents.

小题1:This text is most probably written by _______.

A．a headmaster of a middle school

B．a specialist in teenager studies

C．a parent with teenage children

D．a doctor for mental health problems小题2:The boy on the sofa would most probably be described as _______.

A．lazy

B．quiet

C．unusual　　　　　

D．rude小题3:From the second example we can infer that the parents of the two daughters _______.

A．pay no attention to them

B．feel helpless to do much about them

C．are too busy to look after them

D．have come to hate them小题4:What is the author's opinion about the sudden change in teenage children?

A．Parents have no choice but to try to accept it.

B．Parents should pay still more attention to the change.

C．Parents should work more closely with school teachers.

D．Parents are at fault for the change in their children.

建立职业健康安全与环境管理体系的步骤不包括( )。

A．人员培训

B．领导决策

C．体系文件的编写

D．管理评审

管理费用