问题 选择题

下列说法不正确的是(  )

A.运动物体在某一时刻的速度可能很大而加速度可能为零

B.运动物体在某一时刻的速度可能为零而加速度可能不为零

C.在初速度为正、加速度为正的匀变速直线运动中,当加速度减小时,它的速度也减小

D.在初速度为正、加速度为负的匀变速直线运动中,速度不可能增大

答案

A、运动物体在某一时刻的速度可能很大而加速度可能为零,故A正确

B、运动物体在某一时刻的速度可能为零而加速度可能不为零,例如竖直上抛到最高点,故B正确

C、在初速度为正、加速度为正的匀变速直线运动中,速度一定增加,故C错误

D、在初速度为正、加速度为负的匀变速直线运动中,速度一定减小,故D正确

本题选不正确的故选C.

阅读理解

TUVALU, a tiny country in the Pacific Ocean, has asked for help as it will be swallowed up by the sea.

Storms and huge waves are a constant threat and none of Tuvalu’s nine little islands is more than five meters above sea level. Salt water is already entering the country’s drinking water supply, as well as damaging plants that produce fruit and vegetable. Without urgent help, the country’s days are numbered.

But Tuvalu is not the first place to face sinking into the sea. Venice, a historic city in Italy best known for its canals, has sunk about 24cm over the past 100 years. Experts say that it will have sunk another 20-50cm by 2050. A century ago, St. Mark’s Square, the lowest point city, flooded about nine times a year. Nowadays, it happens more than 100 times. While Venice is slowly sinking into the mud on which it stands, global warming causes Tuvalu’s rising sea level.

The average global temperature has increased by almost 0.5 centigrade degrees over the past century; scientists expect it rise by extra 1-3 degrees over the next 100 years.

Warmer weather makes glaciers (冰川) melt, and adds more water to the ocean. The warmer temperatures also make water expand, so it takes up more space, causing the sea level to rise. The sea level has risen about 10-25 cm in the last 100 years.

The main cause of global warming is human pollution. Through burning coal, oil and gas, people have been increasing the greenhouse gases in the atmosphere, such as CO2. This adds to the power of the greenhouse effect, making the planet even warmer.

Many scientists believe that, if the warming is not stopped, there will be huge climate changes. The sea level could rise by one meter this century.

Should this come true, the sea will swallow up millions of homes and the world will be flooded with “climate refugees” looking for somewhere to live.

68. We can infer from the second paragraph that         .

A. Tuvalu is in danger of being swallowed up by the sea

B. all Tuvalu’s islands are about five meters above the sea level

C. drinking water in Tuvalu has been destroyed

D. Tuvalu is often flooded by storms and waves

69. Put the following events in the right order.

a. Glaciers began to melt.                b. People burn coal ,oil and gas.   

c. The greenhouse effect is growing.       d. The earth is getting warmer and warmer       

e. The sea level is rising.                 f. More CO2 is produced.      

g. Many places are sinking into the sea.

A. d,f,b,c,a,e,g       B. b,f,c,d,e,a,g       C. f,c,b,d,a,e,g       D. b,f,c,d,a,e,g

70. What does “climate refugees” mean?

A. Climate changes.       B. Climate effect.     

C. People forced away from their homeland by climate.   

D. Rare animals moving from place to place for climate changes.

71 Which of the following is False according to the passage?

A. The sea level has risen about 10-25 cm in the last 100 years for warmer       temperatures.

B. The average global temperature has risen by 1-3 centigrade degrees over the past 100 years.

C. The warmer temperature causes the sea level to rise.

D. There will be huge climate changes unless the warming is stopped

单项选择题