問題詳情

五. Reading Comprehension: 30%   A revolution in our understanding of the Earth is reaching its climax as evidence accumulates that the continents of today are not venerable landmasses but amalgams of other lands repeatedly broken up, juggled, rotated, scattered far and wide, then crunched together into new configurations like ice floes swept along the shore of a swift-flowing stream.   After considerable modification this became the now largely accepted concept of “plate tectonics,” explaining much of what is observed regarding our dynamic planet. Some oceans, such as the Atlantic, are being split apart, their opposing coasts carried away from one another at one or two inches per year as lava wells up along the line of separation to form new seafloor. Other oceans, such as the Pacific, are shrinking as seafloor descends under their fringing coastlines or offshore arcs of islands. From the deepest ocean trench to the tallest mountain, plate tectonics explains the features and movement of Earth's surface in the present and the past. Based on the theory of plate tectonics, Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere. Developed from the 1950s through the 1970s, plate tectonics is the modern version of continental drift, a theory first proposed by scientist Alfred Wegener in 1912. Wegener didn't have an explanation for how continents could move around the planet, but researchers do now. The Earth’s crust, in this view, is divided into several immense plates that make up the continents and seafloors, and that all float on a hot,plastic, subterranean “mantle.” What causes these plates to jostle each other, splitting apart or sliding under one another at their edges, is still a mystery to geologists: it may be friction from circulating rock in the Earth’s mantle, or it may be an effect produced by gravity.
36. In the first paragraph, the author mentions ice floes in order to __________.
(A) explain their movement and the speed at which they travel
(B) verify what the weather was like thousands of years ago
(C) show where they are located in relation to continents
(D) illustrate the concept of how continents shift

參考答案

答案：D
難度：適中0.666667
統計：A(1),B(2),C(3),D(12),E(0)

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