問題詳情
Questions 1-9The geology of the Earth's surface is dominated by the particular properties ofwater. Present on Earth in solid, liquid, and gaseous states, water is exceptionallyreactive. It dissolves, transports, and precipitates many chemical compounds and isconstantly modifying the face of the Earth.(5) Evaporated from the oceans, water vapor forms clouds, some of which aretransported by wind over the continents. Condensation from the clouds provides theessential agent of continental erosion: rain. Precipitated onto the ground, the watertrickles down to form brooks, streams, and rivers, constituting what is called thehydrographic network. This immense polarized network channels the water toward a(10) single receptacle: an ocean. Gravity dominates this entire step in the cycle becausewater tends to minimize its potential energy by running from high altitudes toward thereference point that is sea level.The rate at which a molecule of water passes though the cycle is not random but isa measure of the relative size of the various reservoirs. If we define residence time as(15) the average time for a water molecule to pass through one of the three reservoirs-atmosphere, continent, and ocean-we see that the times are very different. A watermolecule stays, on average, eleven days in the atmosphere, one hundred years on acontinent and forty thousand years in the ocean. This last figure shows the importanceof the ocean as the principal reservoir of the hydrosphere but also the rapidity of water(20) transport on the continents.A vast chemical separation process takes places during the flow of water over thecontinents. Soluble ions such as calcium, sodium, potassium, and some magnesium aredissolved and transported. Insoluble ions such as aluminum, iron, and silicon staywhere they are and form the thin, fertile skin of soil on which vegetation can grow.(25) Sometimes soils are destroyed and transported mechanically during flooding. Theerosion of the continents thus results from two closely linked and interdependentprocesses, chemical erosion and mechanical erosion. Their respective interactions andefficiency depend on different factors.
【題組】1. The word "modifying" in line 4 is closest in meaning to
(A) changing
(B) traveling
(C) describing
(D) destroying
參考答案
答案：A
難度：簡單0.818182
統計：A(9),B(0),C(2),D(0),E(0)