如图所示,AB是一质量为m的均匀细直杆,A端靠在光滑的竖直墙壁上,B端置于水平地

题型:选择题

问题:

如图所示,AB是一质量为m的均匀细直杆,A端靠在光滑的竖直墙壁上,B端置于水平地面上,杆身与竖直方向夹角为θ,杆与地面的摩擦系数为μ,保持平衡,则此时杆与地面的摩擦力为(  )

A.mgtgθ

B.mgsinθ

C.μmg

D.μmg

考点:摩擦力的大小摩擦力的种类杠杆的平衡条件
题型:选择题

采购人采购纳入《政府采购自主创新产品目录》中的货物和服务时,应遵循()的规定

A.强制采购

B.直接采购

C.询价采购

D.优先采购

题型:选择题

阅读理解。

     When punctuation (标点) began, it was mainly to help people read out loud. Until a few hundred years

ago, not many people were taught to read, so there was a lot more reading out loud by the few people who

could.

     To help those reading out loud in the old days, sign (符号) known as "points" were added to pages of

writing. Punctuation comes from the Latin word punctus, meaning "point". These points told readers when

to pause (暂停) or take a breath, and what to emphasize (加重).

     In Europe from the early centuries AD, these points were widely used although not everybody used the

same points for the same thing. When printing was invented, printers had to be made more clearly about

what to put where, so that everyone was doing the same thing. Since that point, all sorts of punctuation

rules have been discov ered and invented.

     Speech marks ".."

     Speech marks or quotation marks are used to show that someone is speaking. The sort we have in English

today began to be widely used during the 18 century. Before that readers simply understood from the way a

sentence was written that someone was speaking although sometimes spoken words were underlined.

     Comma, colon: period (full stop).

     All three of these sorts of punctuation marks were given their Greek names by Aristophanes, a librarian

who lived in Byzantium in the 2'd century BC. They were marks on the page, each with a message to the

reader. Comma meant a short pause. Colon meant a medium (中等的) sized pause. Period meant a long pause.

     Exclamation mark!

     In the early days of punctuation, if you saw this sign, you were supposed to pause. Some people think

the exclamation mark began as what the Creek word JO looked like if it was turned 90 degrees. This word

means"Oh, gosh!" With the I on the top and the O under it, the sign as we know it today was developed.

     Question mark?

     In the middle age, a squiggle (圆弧) above a full stop was sometimes used to show the sentence was a

question and that a person's voice should go up at the end. By the 17" century it had turned into what we

call a question mark. The shape may have come from the letter Q short for that Latin quaestio, meaning

"question". 

     Writers make choices about punctuation because they think differently about sentences and words. It's

part of the personality of their writing. Some writers hate punc- tuation, but others love punctuation. So

whether you love or hate punctuation, the best advice may be to just enjoy it, play with it, think about it and

use it. It belongs (属于) to the language and it belongs to you.

1. When did punctuation begin to be widely used, according to the passage?

A. In the 17th century.

B. In the 2nd century BC.

C. In the 18th century.

D. In the early centuries AD.

2. All punctuation rules were discovered and invented in order to ________.

A. help people read out loud

B. meet the need of printing

C. guide the way of writing

D. mention the spoken words

3. Which of the following is true?

A. A long pause comes after question mark.

B. Speech marks were named by a librarian.

C. Question mark comes from a Latin word.

D. The shape of a word makes exclamation mark.

4. What's the problem about punctuation today?

A. People have completely different ideas about it.

B. Not many people are taught to use it correctly.

C. It has different meanings to different people.

D. Sometimes spoken words must be underlined.

题型:选择题

At school Kitty is a __________ student. She is good at all her lessons. [ ]

A. bad

B. top

C. tall

D. healthy

题型:选择题

消防车登高操作场地及其下面的地下室、管道和暗沟等,能承受重型消防车的压力,重系列消防车最大总质量一般为()。

A.15~50t 

B.15~40t 

C.10~50t 

D.10~40t

题型:选择题

根据税权的集中程度,可以把税权划分为()。

A.税权分散制

B.税权集中制

C.税权统一制

D.税权分散和集中结合制

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