机械传动的作用是( )。A．传递动力 B．改变运动速度和方向 C．改变运动形式 D

150 Years of Cool

Look in the bedrooms of young people around the world. You will probably find a pair of blue jeans in each room. Jeans are very popular all over the world.

Jeans give you the feeling of comfort, youth and energy. They have long been liked by every person.

Levi Strauss is an American company. It first made blue jeans. The company was founded in 1853 by 24-year-old Levi Strauss. Twenty years later, he made the first blue jeans in the world. The jeans were used as working trousers for the cowboys of the American West. During the Second World War, American soldiers brought blue jeans to Europe and Asia. People there began to wear jeans. Little by little, they become cool.

People from different countries like different styles of jeans. Americans like to wear simple and single-colored jeans, but many Chinese like to wear jeans with lots of different colors.

Jeans now can be seen everywhere: However, in many places, it’s not always good to wear jeans. No matter how good they may look, or what color they are, it’s often not right to wear jeans in formal places. But, when you are out, relaxing and having fun, jeans are the best choice.

小题1:The story is talking about_____________.

A．Levi Strauss

B．young people

C．cool

D．jeans小题2:Levi Strauss made the first blue jeans_____________.

A．when he was 44

B．when he was 24

C．in 1853

D．in 1924小题3:___________ wore jeans after they were first made.

A．American soldiers

B．American cowboys

C．Levi Strauss

D．The people in Europe小题4:Jeans can be cool for nearly 150 years because _____________.

A．they have different styles

B．they have different colors

C．they make us feel youth, comfort and energy

D．they are working trousers.小题5:When you _____________, you’d better not wear a pair of jeans.

A．go to an important meeting

B．go on a trip

C．have a party

D．are having fun

若将正偶数2，4，6，8，10，12，14，16，……依次排成一行：　　246810121416……　　则从左向右数的第101个数码是（ ）。

A．1

B．2

C．3

D．4

46～50题基于以下题干：
某个实验由8个必要的步骤组成。用3天来做这个实验，每一个步骤需要整个上午或整个下午的时间，每个上午或下午最多只能同时做两步实验，做该实验时必须遵从以下原则：
(1)J必须在第二天进行； (2)P必须在上午进行；
(3)K和M必须同时进行； (4)J必须在M和O之后进行；
(5)O必须在P和S之前进行。

P最早可以在下面哪一个时间段内进行

A．第一天上午

B．第一天下午

C．第二天上午

D．第二天下午

某人利用如图所示滑轮组从井中提水，在某次操作中，人在绳端所用拉力F=50N，在t=10s内将重为90N的水匀速提升6m．求这段时间内：

(1)人所做的有用功；

(2)拉力F做功的功率；

(3)此次操作中装置的机械效率． （摩擦和绳重不计）

“故能驾驭将帅，训齐士卒，外以捍夷狄，内以平中国。”中“中国”指的是（）

A.中原地区

B.我国的领土

C.中部国家

D.中心地区