论文跟踪导练（三）2是关于跟踪方面的论文题目、论文提纲、跟踪论文开题报告、文献综述、参考文献的相关大学硕士和本科毕业论文。
A
Today I’ll be talking about the invention of the camera and photography. The camera is often thought to be a modern invention, but as early as 1727, a German physicist discovered that light darkens silver salt. Used as a camera, a big box was set up, and a all hole was cut in one side to let the light in； he made temporary pictures on the salt. Silver salt is still the base（基础）of the photographic film today. Then a French scientist made the first permanent picture by using a special piece of metal which was covered with silver salt. A photo graph he made in 1826 still exists.
The painter De Gear improved the process by covering the metal as well as placing the common salt which we can eat. This was in 1839, the official date of the beginning of photographs. But the problem was the printing of the photographs. And it wasn’t until other scientists developed the kind of photographic paper we use now that good prints were possible and photo-graphy became truly modern. In the 1870s, Matthew Bradey was able to take his famous pictures in American Civil War. In the 1920s, Georges Mann of the United States simplified film developing（冲洗）, and Dr Edward Lane invented the so-called “Instant Camera” which uses self-developing film. If we say photography came into existence in 1839, it follows that it took more than 100 years for the camera to reach its present condition of technical refinement（密度）.
1. What discovery was the basis of photography?
A. Light darkens silver.
B. Light darkens silver salt.
C. Light darkens natural salt.
D. Light darkens self-developing film.
2. How was the first permanent picture made?
A. By making use of special paper.
B. By using a special piece of metal.
C. By adding common salt to silver salt.
D. By giving a slight colour to the silver salt.
3. Which year is regarded as the official date of the beginning of photography?
A. 1727.B. 1826.
C. 1839.D. 1870.
4. What can we learn about Matthew Bradey according to Paragraph 2?
A. He was a soldier.
B. He painted portraits.
C. He took war photographs.
D. He designed an easy-carried camera.
5. What did Doctor Edward Lane invent?
A. A new kind of film.
B. A self-action printer.
C. A cheap process of developing film at home.
D. An “Instant Camera” that develops its own film.
B
What would you think if I told you I could eat 40 percent more food than other people—eat boxes of ice cream, bowls of noodles and plates of meat—and all the while be losing weight?
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