A. the creation of new entities
B. an explosion of huge stars
C. the tiniest particle
D. the same amount of mass
E. the existence of black holes
F. a fraction of an inch
延伸阅读
你可能感兴趣的试题
The Tough Grass that Sweetens Our Lives
Sugar cane was once a wild grass that grew in New Guinea and was used by local people for roofing their houses and fencing their gardens. Gradually a different variety evolved which contained sucrose and was chewed on for its sweet taste. Over time, sugar cane became a highly valuable commercial plant, grown throughout the world. 46 Sugar became a vital ingredient in all kinds of things, from confectionery to medicine, and, as the demand for sugar grew, the industry became larger and more profitable. 47 Many crops withered and died, despite growers’ attempts to save them, and there were fears that the health of the plant would continue to deteriorate. In the 1960s, scientists working in Barbados looked for ways to make the commercial species stronger and more able to resist disease. They experimented with breeding programmes, mixing genes from the wild species of sugar cane, which tends to be tougher, with genes from the more delicate, commercial type. 48 This sugar cane is not yet ready to be sold commercially, but when this happens, it is expected to be incredibly profitable for the industry. 49 Brazil, which produces one quarter of the world’s sugar, has coordinated an international project under Professor Paulo Arrudo of the Universidade Estaudual de Campinas in Sao Paulo. Teams of experts have worked with him to discover more about which parts of the genetic structure of the plant are important for the production of sugar and its overall health. Despite all the research, however, we still do not fully understand how the genes function in sugar cane. 50 This gene is particularly exciting because it makes the plant resistant to rust, a disease which probably originated in India, but is now capable of infecting sugar cane across the world. Scientists believe they will eventually be able to grow a plant which cannot be destroyed by rust.
A.the 1980s,scientists have been analysing the mysterious of the sugar canes genetic code.
B.Unfortunately,however,the plant started to become weaker and more prone to disease.
C.The majority of the world’s sugar now comes from this particular commercial species.
D.One major gene has been identified by Dr. Angellique D’Hont and her team in Montpeller,France.
E.Eventually,a commercial plant was developed which was 5 percent sweeter than before,but also much stronger and less likely to die from disease.
F.Sugar cane is now much more vigorous and the supply of sugar is therefore more guaranteed.
第一篇
Energy and Public Lands
The United States boasts substantial energy resources. Federal lands provide a good deal of U.S. energy production; the U.S. Department of the Interior manages federal energy leasing, both on land and on the offshore Outer Continental Shelf. Production from these sources amounts to nearly 30 percent of total annual U.S. energy production. In 2000, 32 percent of U.S. oil, 35 percent of natural gas, and 37 percent of coal were produced from federal lands, representing 20,000 producing oil and gas leases and 135 producing coal leases. Federal lands are also estimated to contain approximately 68 percent of all undiscovered U.S. oil reserves and 74 percent of undiscovered natural gas. Revenues from federal oil, gas, and coal leasing provide significant returns to U.S. taxpayers as well as State governments. In 1999, for example, $553 million in oil and gas revenues were paid to the U.S. Treasury, and non-Indian coal leases accounted for over $304 million in revenues, of which 50 percent were paid to State governments. Public lands also play a critical role in energy delivery. Each year, federal land managers authorize rights of way for transmission lines, rail systems, pipelines, and other facilities related to energy production and use. Alternative energy production from federal lands lags behind conventional energy production, though the amount is still significant. For example, federal geothermal resources produce about 7.5 billion kilowatt-hours of electricity per year, 47 percent of all electricity generated from U.S. geothermal energy. There are 2,960 wind turbines on public lands in California alone, producing electricity for about 300,000 people. Federal hydropower facilities produce about 17 percent of all hydropower produced in the United States. Because of the growing U.S. thirst for energy and increasing public unease with dependence on foreign oil sources, pressure on the public lands to meet U.S. energy demands is intensifying. Public lands are available for energy development only after they have been evaluated through the land use planning process. If development of energy resources conflicts with management or use of other resources, development restrictions or impact mitigation measures may be imposed, or mineral production may be banned altogether.
A.the amount of alternative energy production from public lands is huge.
B.alternative energy production is no less than conventional energy production.
C.they are the most typical conventional energy resources from public lands.
D.geothermal resources are more important than the other two.
The Tough Grass that Sweetens Our Lives
Sugar cane was once a wild grass that grew in New Guinea and was used by local people for roofing their houses and fencing their gardens. Gradually a different variety evolved which contained sucrose and was chewed on for its sweet taste. Over time, sugar cane became a highly valuable commercial plant, grown throughout the world. 46 Sugar became a vital ingredient in all kinds of things, from confectionery to medicine, and, as the demand for sugar grew, the industry became larger and more profitable. 47 Many crops withered and died, despite growers’ attempts to save them, and there were fears that the health of the plant would continue to deteriorate. In the 1960s, scientists working in Barbados looked for ways to make the commercial species stronger and more able to resist disease. They experimented with breeding programmes, mixing genes from the wild species of sugar cane, which tends to be tougher, with genes from the more delicate, commercial type. 48 This sugar cane is not yet ready to be sold commercially, but when this happens, it is expected to be incredibly profitable for the industry. 49 Brazil, which produces one quarter of the world’s sugar, has coordinated an international project under Professor Paulo Arrudo of the Universidade Estaudual de Campinas in Sao Paulo. Teams of experts have worked with him to discover more about which parts of the genetic structure of the plant are important for the production of sugar and its overall health. Despite all the research, however, we still do not fully understand how the genes function in sugar cane. 50 This gene is particularly exciting because it makes the plant resistant to rust, a disease which probably originated in India, but is now capable of infecting sugar cane across the world. Scientists believe they will eventually be able to grow a plant which cannot be destroyed by rust.
A.the 1980s,scientists have been analysing the mysterious of the sugar canes genetic code.
B.Unfortunately,however,the plant started to become weaker and more prone to disease.
C.The majority of the world’s sugar now comes from this particular commercial species.
D.One major gene has been identified by Dr. Angellique D’Hont and her team in Montpeller,France.
E.Eventually,a commercial plant was developed which was 5 percent sweeter than before,but also much stronger and less likely to die from disease.
F.Sugar cane is now much more vigorous and the supply of sugar is therefore more guaranteed.
热门相关试卷
最新相关试卷