平面一般力系简化的结果，若主矢等于零，主矩不等于零，则力系简化为一个（）。A、合力B

结合下列两幅图片及所学知识，回答相关问题

图一：雅尔塔会议上的丘吉尔、罗斯福、斯大林	图二：古巴导弹危机

（1）据图一指出当时的美苏两国之间是何种关系？结成这种关系的主要原因是什么？                                                                                                                                                              （2）据图二指出当时的美苏两国是何种关系？这种关系使当时世界形成怎样的政治格局？这一格局结束的标志是什么？                                                                                                                                                              

车身修复中常用的基本测量工具有（）。

A．游标卡尺

B．千分尺

C．扭簧比较仪

D．水平仪

总偏差平方和的自由度fT为（）。

A.14

B.15

C.8

D.12

The National Dark-Sky Week (NDSW) is a week during which people all over the United States turn off their lights to enjoy the beauty of the night sky without light pollution. This even was started by Jennifer Barlow of Midlothian, Virginia in 2003, and it is becoming more popular each year. It has been supported by the International Dark-Sky Association, the American Astronomical Society, and the Astronomical League.

This even always occurs in April, during the week of the new moon so that the sky can be as dark as possible for the best viewing conditions.

“It is my wish that people could see the night sky without other light in the sky as our ancestors (祖先) saw it hundreds of years ago,” explains Barlow.

Since it only lasts a week and not everyone in the country will take part in it, how will the National Dark-Sky Week reduce light pollution? The main goal of NDSW is to increase awareness (意识) of the harmful effects of light pollution. It is not possible for all of the light pollution in this part of the world to disappear. However, it is possible to make a small difference in the quality of the night sky. Another goal of this even is to promote (促进) the use of better lighting systems that direct light toward the ground instead of up into the sky.

Jennifer Barlow states, “The night sky is a gift of such beauty that it should not be polluted by wasted light. In this way, our children will not lose touch with the wonder of our universe.”

小题1:This passage is mainly about ______________.

A．better lighting systems

B．the beauty of the night sky

C．the harm of light pollution

D．the National Dark-Sky Week小题2:Which of the following statements about the National Dark-Sky Week is WRONG?

A．It is becoming more and more popular in America.

B．The event was started in 2003 by Jennifer Barlow.

C．The event takes place in the first week of every April.

D．American people are supposed to turn off their lights during that week.小题3:What is Jennifer Barlow’s wish?

A．That light would be directed up into the sky.

B．That the sky would always be as dark as possible.

C．That people could see the night sky without light pollution as our ancestors did.

D．That people could spend time enjoying the beauty of the sky every night.小题4:We can infer from the underlined（划线的）sentence in Paragraph 4 that ________.

A．many people in America hate this event

B．it may be hard to reduce light pollution

C．the event should last a month every year

D．light will no longer pollute the sky soon小题5:What is the main goal of the National Dark-Sky Week?

A．To promote the use of better lighting systems.

B．To help people realize the harm of light pollution.

C．To cause all the light pollution in America to disappear.

D．To help young children enjoy the wonder of our universe.

DSS的工作方式主要是（）。

A.人机对话方式

B.键盘操作方式

C.交互会话方式

D.非交互会话方式