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单选题 There are many chemicals that are called invisible inks. An example is lead acetate solution whose invisible marks turn dark when treated with hydrogen sulfide. Letters written with lemon juice cannot be read until they are warmed. Then the writing becomes brown. These inks are known also as ______
学科：默认课程
时间：2026-05-27 11:16:03
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题目1单选题
Early in the 1940s a process was discovered that greatly increased the resistance of paper to disintegration when wet. This innovation was constantly refined until wet-strength paper products served such widespread uses as flooring, bathmats, facial tissues, woven or knitted paper fabric for upholstery materials, and many other uses. But perhaps the most popular use, both past and present, to which paper had been put is the making of government-printed rectangular sheets called ______A. invoicesB. moneyC. trading stampsD. circulars
题目2单选题
Before printing was invented, books had to be copied by hand. The copyists were called scribes, and their work was very slow. A wealthy family in Florence employed almost fifty scribes to copy books for its private library. These scribes could produce only about a hundred books a year. Books were only for the ______A. scribesB. richC. poorD. teachers
题目3单选题
There are many chemicals that are called invisible inks. An example is lead acetate solution whose invisible marks turn dark when treated with hydrogen sulfide. Letters written with lemon juice cannot be read until they are warmed. Then the writing becomes brown. These inks are known also as ______A. poison inksB. secret inksC. printing inksD. permanent inks
题目4单选题
Microfilming of records and file material results in great saving of space. The film is tiny, and the contents of an entire book can be put on a very short piece of film. A special film reader makes it easy to enlarge the image of the film so that it can be read easily. Copies of rare books and manuscript can be supplied on microfilm at very low cost. The microfilming process not only saves space; it also saves ______A. camerasB. librariesC. readersD. money
题目5单选题
The papermaking process spread rather slowly in Europe, but the fourteenth century paper had become common. The few books that were made in Europe before 1450 were written by hand. The printing press was invented in the fifteenth century, and the number of books printed by 1500 was over eight million. The tremendous increase in bookmaking, however, could not have taken place if paper had not been ______A. handwrittenB. availableC. whiteD. unknown
题目6单选题
Nowadays, we have machines for making many thing that people used to make by hand. Making things by hand is now popular as a hobby rather than from necessity. Examples of these handicrafts are weaving, bookbinding, knitting, block printing, lace making, and basket weaving. These and other crafts are so widely enjoyed that special shops carry a variety of supplies for handcrafters. These shops are called ______A. chain storesB. supermarketsC. hobby shopsD. variety shops
题目7单选题
The earliest dyes used were natural dyes made from plants or animals. Sometimes the substances for making the dyes had to be brought from great distances and were therefore very expensive. Most dyes now are chemically prepared and are much less expensive. Even low-cost fabrics may now be obtained in ______A. only certain shopsB. a large price rangeC. beautiful shades and tintsD. natural and synthetic fibers
题目8单选题
For almost as long as people have worn clothes, they have been interested in using bright dyes to make their clothes beautiful. The earliest dyes available were derived from plants and animals. Indigo, a blue dye, was made from a plant. A thousand years before the Christian era, in the ancient Phoenician city of Tyre, a purple dye called Tyrian purple was made from a Mediterranean shellfish. The dye was so prized that its manufacture and export made Tyre ______A. richB. AsianC. isolatedD. old
题目9单选题
Game fish cannot live in lakes that become filled with mud and choked with weeds. In order to restore such lakes to their original free state, a new type of dredge has been developed. This huge dredge, which costs less than earlier dredging methods, chews up the weeds, sucks up the bottom mud and muck into a floating pipe, and discharges the debris on the shore. This dredge is called the world's largest vacuum cleaner since, like a household vacuum cleaner, its operating principle is ______A. restoringB. suctionC. electricalD. choking
题目10单选题
In 1785, the French aeronaut, P. Blanchard successfully used a parachute to drop a dog in a basket to the ground from a balloon high in the air. In 1793, Blanchard himself used a parachute to jump from a balloon. His first attempt was not successful — he broke his leg. Others made several attempts, some successful, some not, before parachute jumping came to be common and ______A. safeB. expensiveC. martialD. dangerous
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