【正文】 however, there were not yet efficient means by which to produce mechanical energy or to power machinery. This was to occur with progress in the development of the steam engine. In the late 1700s James Watt designed an efficient and mercially viable steam engine that was soon applied to a variety of industrial uses as it became cheaper to use. The engine helped solve the problem of draining coal mines of groundwater and increased the production of coal needed to powe。s interior rose and formed the mantle, a denser layer of silicates around the core, and the crust, a thinner layer of silicates at Earth39。s lack of an atmosphere explains why it was bombarded with much more frequency and violence than other plaesimals. ? Continued bombardments and internal pressures made the growing Earth hotter, causing its interior to melt and the heavier elements to sink and form Earth39。s interior rose and formed the mantle, a denser layer of silicates around the core, and the crust, a thinner layer of silicates at Earth39。s lack of an atmosphere explains why it was bombarded with much more frequency and violence than other plaesimals. ? Continued bombardments and internal pressures made the growing Earth hotter, causing its interior to melt and the heavier elements to sink and form Earth39。s core. Much of the early continental crust has remained on 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 surface, the lightest silicates rose to Earth39。s surface. ? It lacked water vapor. Paragraph 3: As heavy materials headed for the center of Earth, lighter silicates (such as the mineral quartz) drifted upward. The denser silicates formed Earth39。s first stable atmosphere. 11. The word emitted in the passage is closest in meaning to ? Released ? Consumed ? Contained ? Heated 12. What can be inferred from paragraph 4 about 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 size ? caused the temperatures of Earth39。s continental crust ? has changed significantly in position over time ? was as thick as Earth39。s core. Much of the early continental crust has remained on 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 surface, the lightest silicates rose to Earth39。s core is mostly iron because, pared to most other elements on early Earth, iron ? was denser ? melted more easily ? was more radioactive ? was more plentiful Paragraph 3: As heavy materials headed for the center of Earth, lighter silicates (such as the mineral quartz) drifted upward. The denser silicates formed Earth39。s core was nickel ? What internal pressures caused Earth to heat up as it grew in size ? What caused Earth39。s atmosphere, we must go back to the earliest days of the solar system, before the plas themselves were formed from a disk of rocky material spinning around the young Sun. This material gradually coalesced into lumps called plaesimals as gravity and chance smashed smaller pieces together, a chaotic and violent process that became more so as plaesimals grew in size and gravitational pull. Within each orbit, collisions between plaesimals generated immense heat and energy. How violent these processes were is suggested by the odd tilt and spin of many of the plas, which indicate that each of the plas was, like a billiard ball, struck at some stage by another large body of some kind. Visual evidence of these processes can be seen by looking at the Moon. Because the Moon has no atmosphere, its surface is not subject to erosion, so it retains the marks of its early history. Its face is deeply scarred by millions of meteoric impacts, as you can see on a clear night with a pair of binoculars. The early Earth did not have much of an atmosphere. Before it grew to full size, its gravitational pull was insufficient to prevent gases from drifting off into space, while the solar wind (the great stream of atomic particles emitted from the Sun) had already driven away much of the gaseous material from the inner orbits of the solar system. So we must imagine the early Earth as a mixture of rocky materials, metals, and trapped gases, subject to constant bombardment by smaller plaesimals and without much of an atmosphere. 1. The word coalesced in the passage is closest in meaning to ? Collided ? Joined ? Changed ? Shrank 2. The word chaotic in the passage is closest in meaning to ? Rapid ? Disanized ? Intense ? Longlasting 3. All of the following are true of the plaesimals mentioned in paragraph 1 EXCEPT: ? They were formed of rocky material spinning around the early Sun. ? They collided violently with each other. ? They gradually grew in size. ? They lost their atmospheres as they were hit by larger bodies. 4. The word retains in the passage is closest in meaning to ? Reveals ? Acquires ? Hides ? Preserves 5. The author discusses the Moon in paragraph 1 in order to ? Help explain why Earth had fewer meteoric impacts than other plas in the solar system ? Show why