液控单向阀，当控制油口K处无压力油通入时，它的工作原理与普通单向阀（）；当油口K通入

阅读理解。

     The continent of Africa has a long history and a rich culture,and this is shown in traditional dress. You

 often find three colours-red, gold and green-in the clothing．The first colour stands for (象征) the blood

  of millions of people who suffered as slaves (奴隶); the second is for the rich resources (资源) of the

  African earth; and the third represents the grasslands of home．

     Because clothing has a strong social meaning, people are very careful in choosing what to wear. It

 would be a serious mistake to wear the wrong clothing, or to wear clothes in the wrong way. For

  example, in Ghana, a woman should wear her waistband (腰带) differently according to the importance

 of the social event.

     Traditional dress also tells us about everyday life. African designs are famous for loose (宽松的)

 clothing. Tile climate, with the hot sun and wide temperature ranges (变化), requires that the clothes are

  comfortable for daily life.

     Although many people wear Western clothes,particularly in the big cities in Africa,traditional African

 dress is very highly valued. This is because it has deep cultural meanings.

1. The passage is mainly about _____.

    A. the history of clothes in Africa        

    B. modern fashion styles in Africa

    C. the meanings of traditional dress in Africa  

    D. the materials used in traditional dress in Africa

2. According to the passage,red _____.

    A. represents the setting sun                  

    B. stands for the African earth

    C. is chosen because it is a bright colour        

    D. is a reminder of the sad history in Africa

3. Traditional dress should also be practical because _____.

    A. it needs to keep people dry in the rainy season  

    B. it needs to protect people from the climate

    C. people wear it in the big cities            

    D. it has deep cultural meanings

当质量和环境体系被一起审核时，称为( )审核。

A．结合

B．联合

C．合作

D．共同

下列关于生物多样性的叙述中，正确的是（）

A.生物多样性就是指物种多样性

B.就地保护是保护生物多样性的有效措施之一

C.外来物种入侵增加了本地生物多样性

D.保护生物多样性意味着禁止对生物资源的开发利用

一艘船长为35.0米航行A级航区的客船，设置一根管子穿过防撞舱壁以处理首尖舱的液体，穿过防撞舱壁的管子，（）设有在干舷甲板以上控制的截止阀。

在黑屏的情况下呈现的RGB点叫做亮点