液体对浸在其中的物体的压强方向都是竖直向下的[ ]

在现金持有量的随机模式中，下列（）因素的变动可以提高最优现金返回线。

A．降低每次有价证券的固定转换成本

B．提高有价证券的日利息率

C．提高预期每日现金余额变化的标准差

D．降低现金存量下限

下列各组物质中，不属于同分异构体的是

A．和

B．和

C．

D．和

油价正在飞速上涨，我们不能坐以待毙．如图所示，就是网络上流行的一种马拉车，让大家体现一下悍马的概念（g取10N/kg）．

（1）假设该马以2×10³N的力拉着这辆1500kg的汽车向左做匀速直线运动，则路面对汽车的阻力为______N；，方向为______．

（2）汽车受到路面的支持力为______N，说出你的判断理由______．

（3）如果马拉着汽车沿原路返回时车速越来越快，则此时路面对汽车的阻力______（选填“小于”、“大于”或“等于”）马对汽车的拉力．

涡流式位移传感器所配的转换器的输出信号为（）。

A、0～10mA；

B、4～20mA；

C、0～10V；

D、－4～20V。

阅读理解。

     A The story of English language is a story of change. The old English language, or old English, is quite

different from Modern English. If we do not study old English, we can't understand it. Some of the words

are the same, but many are not used now. The story of the English language begins some time after the year

400 AD. At this time, some people came to England from North-west Europe. There were many groups of

people. They were called Angles (盎格鲁人), Saxons (撒克逊人) and Jutes (朱特人), whose language, old

English, is like some of the modern language of North-West Europe. In old English, the ending had many

meanings. They showed past time and present time and many other things. In Modern English, most of these

endings are gone. This is the biggest difference between Old and Modern English.

1. What does the first sentence of the passage mean? [ ]

A. The story of English language often changes.

B. English is a language that has changed a lot as time passes by.

C. The old English language has changed into Modern English.

D. The story of English language is one of how people change the language.

2. Old English has a story of ____. [ ]

A. 2,500 years

B. more than 1,600 years

C. 2,300 years

D. more than 400 years

3. Old English was first used by the people from ____. [ ]

A. Old English

B. English

C. North-West English

D. North-West Europe

4. Which of the following is NOT true about Old English? [ ]

A. The endings of words gave different special meanings.

B. It is easy for most English-speakers today to understand the language.

C. Its words are completely different from those Modern English.

D. It was spoken by many groups of the people from North-West Europe.