已知△ABC为等腰三角形,①当它的两个边长分别为8cm和3cm时,它的周长为(

题型:填空题

问题:

已知△ABC为等腰三角形,①当它的两个边长分别为8cm和3cm时,它的周长为(    )cm;②如果它的周长为18cm,一边的长为4cm,则腰长为(    )cm.

考点:等腰三角形的性质,等腰三角形的判定
题型:填空题

可用作超临界流体的气体很多,其中最为常用的是()

A.CO

B.CO2

C.N2

D.O2

题型:填空题

如下图所示,在探究“物体动能的大小与哪些因素有关”的实验中,让同一铁球从同一斜面的不同高度由静止释放,撞击同一木块.请回答下列问题:

(1)该实验目的是研究动能与           的关系。

(2)该实验是通过观察                   来说明物体动能的大小。

(3)实验中铁球从同一斜面的不同高度由静止释放的目的是__________________ 。

(4)若水平面绝对光滑,该实验能得出结论吗?     ____    (填“能”或“不能”)理由是:              ___            

题型:填空题

阅读理解。

     Lights on thousands of miles of major roads in England could be dimmed (变暗)

    during quiet periods in a bid to save money and reduce carbon emissions from various

  vehicles.

      The Highways Agency suggests reducing light levels on A-roads when traffic levels

  Are" very low".  I:ocal transport minister Norman Baker said he supported the. Move on

  condition. that safety was not compromised.

      Research into when and where lights could be dimmed will begin in May,2012.

      Mr.Kawczynski, a MP (国会议员), asked Transport Minister Norman  Baker

  "what plans he has to change guidance on the, minimum amount of lighting required on A

  roads".  In reply, Mr. Baker wrote:"The Highways Agency has plans to reduce the

  level of lighting on A-roads when traffic levels are far below road capacity.  The agency

  has no plans to reduce the level of lighting on A-roads during the peak (高峰) periods

  that occur during the hours of darkness or to temporarily switch A-roads lighting off

  when traffic flows  are  low. "The  level  of  light. reduction will  be  based upon

  internationally agreed standards and made after discussion and  agreement with the UK's

  Institution of Lighting Professionals."

      Mr. Baker added:"It is right that lighting authorities consider, in the interests of

  cost-saving and the environment, whether lighting can be sensibly dimmed or turned off .

  with proper safety brought into full consideration."

     A Highways Agency spokesman said:"This is not about switching off lights on A-

roads.  Any changes to light level will be determined after discussion and agreement

with industry experts and will meet internationally agreed standards to ensure there will

be no influence on safety for road users."

1.  What is the text mainly about?

A.  A bid for cost-saving and the environment by cutting light levels.

B.  A research on when and where to reduce the light levels.

C.  A discussion about changing the standard of lighting.

D.  A move on the safety of A-roads.

2. Lights on major roads in England could be dimmed _____.  

A. in broad daylight.

B.  during the peak periods

C.  when traffic levels are very low  

D.  when there is power failure

3.   According to Mr. Baker, the level of light reduction will_. 

A.  be determined after discussion and agreement with industry experts

B.  be made only after discussion and agreement with the MP

C.  surely have much influence on safety for road users

D.  be based on internationaay agreed standards

4.   It can be inferred from the passage that

A.  major roads in Britain may be less safer after reducing light levels

B.  air pollution in Britain is becoming a big headache

C.  Britain is suffering from heavy traffic

D.  Britain is faced with a shortage of power

题型:填空题

汽轮机启动暖管时,注意调节送汽阀和疏水阀的开度是为了()。

A、提高金属温度;

B、减少工质和热量损失;

C、不使流入管道的蒸汽压力、流量过大,引起管道及其部件受到剧烈的加热;

D、不使管道超压。

题型:填空题

一个四边形去掉一个角,还剩几角 下列不可能的是:

A.3

B.4

C.5

D.6

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