设n为正整数,坐标平面上有一等腰三角形,它的三个顶点分别是(0,2)、(1n,0

题型:填空题

问题:

设n为正整数,坐标平面上有一等腰三角形,它的三个顶点分别是(0,2)、(
1
n
,0)、(-
1
n
,0),设此三角形的外接圆直径长等于Dn,则
lim
n→∞
Dn
=______.
考点:函数的极值与导数的关系
题型:填空题

中国居民由食物中所摄取的营养素,以()所占比重最大。

A.碳水化合物

B.脂类

C.蛋白质

D.矿物质

题型:填空题

A euphemism (from the Greek words eu—well and pheme—speak) is a word or expression that is used when people want to find a polite or less direct way of talking about difficult or embarrassing topics like death or the bodily functions.Most people,for example,would find it very difficult to say in plain language that they have arranged for their sick old dog to be killed.They would soften the pain by saying:We had Ruby put down or We had Ruby put to sleep.Many people prefer to call someone plain than ugly,or cuddly rather than fat.

Euphemisms are an important part of every language,but it seems that English has an ever­growing number of them.The non­native speaker not only has to make sense of the euphemisms he hears,he also has to learn which euphemisms are appropriate in any particular situation.He might be aware that his American friend needs to use the toilet when she asks where the bathroom (or restroom,or comfort station) is,but he is less likely to guess that his English friend has the same need when he says he has to see a man about a dog.He might have learned,for example,that in the family way is a euphemism for pregnant.If,however,he says to his boss,“Congratulations!I hear your wife is in the family way,” he would be using an expression that is too familiar for the circumstances.

Schools are full of euphemisms.At Frankfurt International School,for example,the special lessons given to students who are having difficulties in their school subjects are called Study Center (in the middle school) and Academic Workshop (in the high school).Teachers rightly do not want to upset students or parents by being too frank or straightforward,and usually choose a softer word or expression to convey the same message.

小题1:According to the passage,people use euphemisms in order to________.

A.make themselves understood

B.avoid embarrassment

C.to sound straightforward

D.attract attention小题2:A person who is described as plain and cuddly is in fact________.

A.tall and handsome 

B.pretty and slim

C.ugly but tall 

D.ugly and fat小题3:When an English lady says she has to see a man about a dog,she might want to________.

A.have her old dog killed 

B.see an ugly friend

C.go to the toilet

D.see a pregnant woman小题4:The main purpose of Paragraph 2 is to________.

A.stress that euphemisms are an important part of every language

B.inform readers that English has an ever­growing number of euphemisms

C.suggest non­native speakers use euphemisms as often as possible

D.warn English learners to be careful about the meaning and use of euphemisms小题5:At Frankfurt International School,the students who receive lessons in Study Center________.

A.have poor grades in the subjects

B.do well in school

C.work hard at their lessons

D.prefer to learn more

题型:填空题

试述破伤风的病理生理改变。

题型:填空题

关于玻璃板液位计的失灵原因,下列说法不正确的一项是()。

A、引出阀关闭

B、玻璃板破

C、引出阀堵

D、液位波动过大

题型:填空题

脉冲仓顶除尘器是由()组成。

A、上箱体;

B、下箱体;

C、清灰系统;

D、除尘系统。

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