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三、根据短文内容，选择正确答案。
When we make ice cream, we need to put salt and ice in a big bag. Why? Because ice melts at 0℃. But when we add salt to ice, the salt lowers（降低） the freezing point of the ice. The ice becomes colder, maybe -10℃ or lower! This super-cold ice can take heat away from the cream mixture very quickly. So the cream mixture freezes into ice cream soon.
We also use salt to melt ice on roads in winter. The salt makes the ice melt faster. So cars can drive safely on the roads. Salt is really useful!
（
A. To make the ice cream sweet.
B. To make the ice colder.
C. To make the ice melt faster.
（
A. 0℃.
B. Higher than 0℃.
C. Lower than 0℃.
（
A. take heat away
B. add heat to
C. take sugar away
（
A. To make ice cream.
B. To melt ice on roads.
C. To make drinks.
（
A. How to make ice cream.
B. The uses of salt.
C. How salt helps change ice.
When we make ice cream, we need to put salt and ice in a big bag. Why? Because ice melts at 0℃. But when we add salt to ice, the salt lowers（降低） the freezing point of the ice. The ice becomes colder, maybe -10℃ or lower! This super-cold ice can take heat away from the cream mixture very quickly. So the cream mixture freezes into ice cream soon.
We also use salt to melt ice on roads in winter. The salt makes the ice melt faster. So cars can drive safely on the roads. Salt is really useful!
（
B
）1. Why do we add salt to ice when making ice cream?A. To make the ice cream sweet.
B. To make the ice colder.
C. To make the ice melt faster.
（
C
）2. What is the freezing point of ice with salt?A. 0℃.
B. Higher than 0℃.
C. Lower than 0℃.
（
A
）3. The super-cold ice can take heat away
from the cream mixture.A. take heat away
B. add heat to
C. take sugar away
（
B
）4. What do people use salt to do in winter?A. To make ice cream.
B. To melt ice on roads.
C. To make drinks.
（
B
）5. What is the main idea of the passage?A. How to make ice cream.
B. The uses of salt.
C. How salt helps change ice.
答案
1. B 2. C 3. A 4. B 5. B
