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问题 不定项选择

在表格中的某一个单元格内输入文字后，要将插入点移到下一个单元格中，可以（）.

A．鼠标单击下一个单元格

B．按“Tab”键

C．按“Shift+Tab”键

D．按向右的箭头键

答案

参考答案：A, B, D

选择题
下列实验方案的设计中，可行的是（　　）

A．向某溶液中滴加BaCl2溶液，出现白色沉淀，再加足量稀HCl，若白色沉淀不溶解，则说明原溶液中一定含SO42-

B．某气体通入澄清石灰水溶液能使其变浑浊，该气体一定是CO2

C．向某盐溶液中滴加NaOH溶液并加热，产生使湿润的红色石蕊试纸变蓝的气体，则原溶液含NH4+

D．某气体通入滴有紫色石蕊试剂的水中，若水变为红色，该气体一定是SO2

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单项选择题

B


Each year there is an increasing number of cars on roads and street are millions of new cars are produced. One out of every six Americans works at putting together the parts of cars, driving trucks, building roads of filling cars with gas. Americans won’t live without cars!
Most Americans find it hard to think what life would be without a car. However some have realized the serious problem of air pollution by cars. The polluted air is poisonous(有毒的) and dangerous to health.
One way to get rid of(排除)the polluted air is to build a new kind of car. That’s what several of the large car factories are trying to do. But to build a clean car is easier said than done. Progress in this field has been slow.
Another way is to take the place of the car engine(发动机) by something else. Engineers are now working on some new cars. Many makers believe that it will take years to develop a practical model that pleases man.
To prevent the world from being polluted by cars, we’ll have to make some change in the way many of us live. Americans, for example, have to cut down on the number of their cars. They are encouraged to travel and go to work by bike. Riding a bike is thought to help keep the air clean.
But this change does not come easily — a large number of workers may find themselves without jobs if a car factory closed down. And the problem of air pollution would become less important than that of unemployment(失业).
Although cars have brought us a better life, they have also brought us new problems.

Some large car factories in the USA are trying to build a new kind of car which ______.

A．is clean in itself

B．is used to clean streets

C．does not pollute the air

D．is easier to make
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