快速性心律失常哪一种表现不属血流动力学不稳定的情况（） A.神志改变 B.心悸

Young people can have problems with their minds. Some students become worried because they have to study very hard. Others have trouble getting on well with people like their parents and classmates.

Liu Wei, a Junior 2 student from Hefei, could not understand his teacher and was doing badly in his lessons. He became so worried about it that he started to cut his finger with a knife.

Another student, 14-year-old Yan Fang from Guangzhou, was afraid of exams. She got very worried in one, and when she looked at the exam paper. She couldn’t think of anything to write.

A recent report from Jiefang Daily says about 18% of Shanghai teenagers have mental （心理的，精神的）problems. Their troubles include（包括）bring worried and very unhappy. And having problems in learning and getting on with people. Many students who have problems won’t go for advice （劝告）or help. Some think they will look stupid（愚蠢）if they go to see a doctor. Others don’t want to talk about their secret.

Liang Yuezhu, an expert on teenagers from Beijing Anding Hospital, has the following advice for teenagers:

*Talk to your parents or teachers often

*Take part in group activities and play sports

*Go to see a doctor if you feel unhappy or unwell

小题1:The students who often become worried or have trouble getting on with others may have _______.

A．mental problems

B．a headache

C．knives with them

D．no parents小题2:Liu Wei cut his finger with a knife because ________.

A．he was afraid of his teacher

B．he wanted to frighten his parents

C．he was so worried about his studies

D．his finger was badly hurt小题3:Yan Fang’s problems happened whenever ________.

A．she studied very hard

B．she had exams

C．she talked with her parents

D．she thought of something小题4:Students who have problems won’t ask others for help because ________.

A．they won’t let others think they are stupid

B．they don’t think doctors can help them

C．they don’t want to tell their secret to others

D．both A and C小题5:Liang Yuezhu’s advice tells us that ________.

A．it’s better for the students who have mental problems to join others

B．it’s unnecessary for them to be with others

C．only group activities and sports can help them

D．teachers and parents can’t do anything about mental problems

已知函数f(x)=mx^m-n的导数为f′(x)=8x³,则mⁿ=　　　　. 

补全对话。从方框中选择最佳选项完成对话，有两项多余。
	A. No, she isn't English. B. How old are you? C. Look at the girl in the picture. D. Her name is Julia Roberts. E. And she is a famous singer (歌手). F. Are you her friend? G. She is Britney Spears.

Zhang Yi: Hello, Tom!  __1__
Tom: Oh, I know her.
Zhang Yi: What's her name?
Tom:  __2__ Britney is the given name and Spears is the family name.
Zhang Yi: Is she English?
Tom:  __3__
Zhang Yi: Where is she from?
Tom: America.  __4__ She sings very well.
Zhang Yi: How old is she?
Tom: She's twenty-eight years old.
Zhang Yi:  __5__
Tom: No, I am not her friend. She is my favourite singer.

质量为m＝1.0 kg的小滑块（可视为质点）放在质量为M＝3.0 kg的长木板的右端，木板上表面光滑，木板与地面之间的动摩擦因数为μ＝0.2，木板长L＝1.0 m。开始时两者都处于静止状态，现对木板施加水平向右的恒力F＝12 N，如图所示，经一段时间后撤去F。为使小滑块不掉下木板，试求：水平恒力F作用的最长时间。（g取10 m/s²）

电气设备试验规定中对发变组保护控制回路的试验要求是？