单选题The foundation of all other branches of mathematics is arithmetic, _ science of calculating with numbers.

单选题The Louisiana Purchase of 1803 increased the territory of the United States by approximate 846,000 square miles, practically doubling the area of the United States.

单选题When swollen by melting snow or heavy rain, some rivers routinely overflow its banks.

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单选题What was special about flint enamel?

单选题The word "Undoubtedly" in line I is closest in meaning to

单选题The (chemical element) chlorine is a corrosive, greenish-yellow gas (that) has (sharp) odor and (has) 21/2 times heavier than air.

单选题1 Alligators have no natural predators except humans. In fact, humans drove alligators to near extinction in many of their marsh and swamp habitats in North America. Hunters once killed large numbers of these animals for their meat and soft belly skin, which was used to make shoes, belts, and wallets. Between 1950 and 1960, hunters wiped out 90 percent of the alligators in Louisiana and greatly reduced the alligator population in the Florida Everglades. 2 In 1967 the federal government placed the American alligator on the endangered species list. In the next decade, protected by hunters and averaging about 40 eggs per nest, the alligator made a strong comeback. It was reclassified from endangered to threatened in Florida, Louisiana, and Texas, where the vast majority of the animals live. As a threatened species, it is still protected from excessive harvesting by hunters; however, limited hunting is allowed in some areas to keep the population from growing too large.

单选题The computer's complex circuitry is miniaturized inside silicon chips, wafer-thin silicon crystals with circuits electronic etched onto them

单选题During the 1850', reform movements _____temperance and the abolition of slavery gained strength in the United States.

单选题What does the passage mainly discuss? (a) Pasteur's influence on the development of the microscope. (b) The origin of the theory of spontaneous generation. (c) The effects of pasteurization on food. (d) Pasteur's argument against the theory of spontaneous generation.

单选题Astronauts receive extensive training to prepare themselves both physically and psychologically for complexity and rigor of a space mission.

单选题Listentopartofalectureinajournalismclass.Nowgetreadytoanswerthequestions.Youmayuseyournotestohelpyouanswer.

单选题Some marine invertebrates, (such as the. sea urchin and the starfish, (migrates) from deep water (to shallow) during spring and early summer (to spawn). A. such as the B. migrates C. to shallow D. to spawn

单选题There are about 350 species and subspecies of birds in danger of become extinct, with a large number of them, 117 in all, found on oceanic islands.

单选题At the college level, the best preparation for management is a liberal arts education. Individuals who will guide the future of their companies must broaden and deepen their understanding of the world. This means covering the whole range of the liberal arts, from science to literature to mathematics to history. Today's executives must have some grasp of economic realities and the political process, as well as some comprehension of the basic framework within which scientific and technological changes take place. They must gain an understanding of human nature, including its negative aspects, such as the sources of human conflict and the pitfalls of power.

单选题Listen to Track 94. A. She is certain about the correct answer. B. She is now aware that her original idea had a weakness. C. She is not convinced that the professor is right. D. She thinks that the professor misunderstood what she said earlier.

单选题Silicon chips are reliable and cheap to produce in large numbers and are used them in computers, calculators, programmed household appliances, and most electronic applications.

单选题While photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.