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简述颜料在涂料中的作用。

答案

参考答案：

颜料是涂料的次要成膜物质，它不仅使涂膜呈现必要的色彩，遮盖被涂物的底层，使涂膜具有装饰性，更重要的是它能改善涂料的物理及化学性能，提高涂膜的机械强度、附着力和防腐性能。有的颜料还可以滤去紫外线等有害光波，从而增强涂膜的耐候性和保护性，延长涂膜的使用寿命。

选择题

在做托里拆利实验时，测得的大气压比真实值小，其原因可能是（　　）

A．玻璃管倾斜

B．玻璃管粗细不均匀

C．水银槽内的水银太多

D．玻璃管内混入少量空气
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单项选择题

"Sesame Street" has been called "the longest street in the world". That is because the television program by that name can now be seen in: so many parts of the world. That program became one of American’s exports soon after it went on the air in New York in 1969.
In the United States more than six million children watch the program regularly. The viewers include more than half the nation’s preschool children, from every kind of economic, racial, and geographical group.

The best title for this passage can be ______.
A. TV Programs
B. Educating Children
C. Sesame Street
D. A Great Success

Although some educators object to certain elements in the program, parents praise it highly. Many teachers also consider it a great help, though some teachers find that problems arise when first graders who have learned from "Sesame Street" are in the same class with children who have not watched the program.
Tests have shown that children from all racial, geographical, and economic backgrounds have benefited from watching it. Those who watch it five times a week learn more than occasional viewers. In the US the program is shown at different hours during the week in order to increase the number of children who can watch it regularly.
The programs all use songs, stories, jokes, and pictures to give children a basic understanding of numbers, letters and human relationships. But there are some differences. For example, the Spanish program, produced in Mexico City, devotes more time to teaching whole words than to teaching separate letters.
Why has "Sesame Street" been so much more successful than other children’s shows Many reasons have been suggested. People mention the educational theories of its creators, the support by the government and private businesses, and the skillful use of a variety of TV tricks. Perhaps an equally important reason is that mothers watch it along with their children. This is partly because famous adult stars often appear on it. But the best reason for: the success of the program may be that it makes every child watching feel able to learn. The child finds himself learning, and he wants to learn more.
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