【正文】 early Earth contained abundant radioactive materials, also a source of heat. As Earth heated up, its interior melted. Within the molten interior, under the influence of gravity, different elements were sorted out by density. By about 40 million years after the formation of the solar system, most of the heavier metallic elements in the early Earth, such as iron and nickel, had sunk through the hot sludge to the center giving Earth a core dominated by iron. This metallic core gives Earth its characteristic magic field, which has played an extremely important role in the history of our pla. As heavy materials headed for the center of Earth, lighter silicates (such as the mineral quartz) drifted upward. The denser silicates formed Earth39。s surface, the lightest silicates rose to Earth39。s interior. These lighter materials, such as the rocks we call granites, formed a layer of continental crust about 35 kilometers thick. Relative to Earth as a whole, this is as thin as an eggshell. Seafloor crust is even thinner, at about 7 kilometers。s core. Much of the early continental crust has remained on Earth39。s interior to the surface. So we can imagine the surface of the early Earth as a massive volcanic field. And we can judge pretty well what gases bubbled up to that surface by analyzing the mixture of gases emitted by volcanoes. These include hydrogen, helium, methane, water vapor, nitrogen, ammonia, and hydrogen sulfide. Other materials, including large amounts of water vapor, were brought in by etary bombardments. Much of the hydrogen and helium escaped。s first stable atmosphere. Paragraph 1: In order to understand the origin of Earth39。s spin and tilt are unique among other plaary bodies in the solar system 6. The word constant in the passage is closest in meaning to ? Considerable ? Unpredictable ? Continual ? Violent Paragraph 2: As it began to reach full size, Earth heated up, partly because of collisions with other plaesimals and partly because of increasing internal pressures as it grew in size. In addition, the early Earth contained abundant radioactive materials, also a source of heat. As Earth heated up, its interior melted. Within the molten interior, under the influence of gravity, different elements were sorted out by density. By about 40 million years after the formation of the solar system, most of the heavier metallic elements in the early Earth, such as iron and nickel, had sunk through the hot sludge to the center giving Earth a core dominated by iron. This metallic core gives Earth its characteristic magic field, which has played an extremely important role in the history of our pla. 7. Paragraph 2 answers which of the following questions about early Earth ? What caused materials on Earth to bee radioactive ? What percentage of Earth39。s magic field 8. According to paragraph 2, Earth39。s mantle, a region almost 3,000 kilometers thick between the core and the crust. With the help of bombardment by ets, whose many impacts scarred and heated Earth39。s surface, where they cooled more rapidly than the better insulated materials in Earth39。 thus, even continental crust reaches only about 1/200th of the way to Earth39。s surface to the present day. 10. According to paragraph 3, Earth39。s mantle in its early stages ? is very thin relative to Earth39。s early core and mantle to gradually increase Paragraph 4: The lightest materials of all, including gases such as hydrogen and helium, bubbled through Earth39。 but once Earth was fully formed, it was large enough for its gravitational field to hold most of the remaining gases, and these formed Earth39。s first stable atmosphere? ? It existed before Earth was yet fully formed. ? It contained very little hydrogen and helium. ? It contained only materials that had bubbled up through Earth39。s mantle, a region almost 3,000 kilometers thick between the core and the crust. With the help of bombardment by ets, whose many impacts scarred and heated Earth39。s surface, where they cooled more rapidly than the betterinsulated materials in Earth39。 thus, even continental crust reaches only about 1/200th of the way to Earth39。s surface to the present day. ■ 13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Even some of its oldest portions as old as billion years can still be found in parts of Canada, Australia, South Africa, and Greenland. 14. Directions: An introductory sentence for a brief summary of the passage of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This questions is worth 2 points. Drag your choices to the spaces where they belong. Answer Choices ? Early Earth39。s core. ? Lighter elements from Earth39。s surface. ? Early Earth39。s core. ? Lighter elements from Earth39。s surface. TPO363 Energy and the industrial Revolution For years historians have sought to identify crucial elements in the eighteenthcentury rise in industry, technology, and economic power known as the Industrial Revolution, and many give prominence to the problem of energy. Until the eighteenth century, people relied on energy derived from plants as well as animal and human muscle to provide power. Increased efficiency in the use of water and wind helped with such tasks as pumping, milling, or sailing. However, by the eighteenth century, Great Britain in particular was experiencing an energy shortage. Wood, the primary source of heat for homes and industries and also used in the iron industry as processed charcoal, was diminishing in supply. Great Britain had large amounts of