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问题 填空题

如图实验，将装有二氧化碳的试管倒放装石蕊的烧杯中．

（1）可观察到的现象有：　_________　；

（2）反应方程式是：　_________　．

答案

（1）紫色石蕊试液变成红色；试管内液面上升

（2）CO2+H2O==H2CO3

选择题

如图所示的五种物质分别是单质、氧化物、酸、碱、盐中的某一种，它们之间的反应关系如图所示，图中两圆相交部分（a、b）是物质间反应的有关内容．

下列说法中错误的是（　　）

A．a处形成浅绿色溶液

B．b反应放热

C．X可能是硫酸镁

D．Y可能为二氧化碳
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单项选择题

Believe it or not，optical illusion can cut highway crashes.
Japan is a case in point．It has reduced automobile crashes on some roads by Rearly 75 percent using a simple optical illusion．Butst．ripes,called chevrons(人字形)，painted on ther rads make drivers think that they are driving faster than they really are，and thus drivers slow down.
Now the American Automobile Association Foundation for Traffic Safety in Washington D．C. is planning t。repeat Japan’s success．Starting next year，the foundati。n will paint cheyrons and。ther pattems of stripes on selected roads around the country to test how well the patterns reduce highway erashes．
Excessive(too great)speed plays a major role in as much as one fifth of all fatal traffic accidents， according to the foundation．To help reduce those accidents，the foundation will conduct its tests in areas where speed-related hazards(danger)are the greatest curves，exit slopes，traffic circles，and bridges．
Some studies suggest that straight，horizontal bars painted across roads can initially cut the average speed of drivers in half．However,traffic。ften returns to full speed within months as driVers become used to seeing the painted bars．
Chevrons，scientists say，not only give drivers the impression that they are driving faster than they reallv are but als0 make a lane appear to be narrower．The result is a longer lasting reduction in highway speed and the number of traffic accidents．

The American Automobile Association Foundation for Traffic Safety plans to______

A. try out the Japanese method in certain areas
B. change the road signs across the country
C. replace straight, horizontal bars with chevrons
D. repeat the Japanese road patterns
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