根据网考网考试中心的统计分析，以下试题在2019/6/4日托福考试习题练习中，答错率较高，为：44%
【单选题】
1Two conditions are necessary for the formation of ice: the presence of water and temperatures below freezing. Ice in the atmosphere and on the ground can assume various forms, depending on the conditions under which water is converted to its solid state~ Ice that forms in the atmosphere can fall to the ground as snow, sleet, or hail. Snow is an assemblage of ice crystals in the form of flakes; sleet is a collection of frozen raindrops, which are actually ice pellets. Hail consists of rounded or jagged lumps of ice, often in layers like the intemal structure of an onion. Ice also forms directly on the ground or on bodies of water. In NorthAmerica, ice forms in late autumn, winter, and early spring. On very large bodies of water, it may not form until late winter because there must be several months of low temperatures to chill such large amounts of water.
2On puddles and small ponds, ice first freezes in a thin layer with definite crystal structure that becomes less apparent as the ice thickens. On lakes large enough to have waves, such as the Great Lakes, the first ice to form is a thin surface layer of slush, sometimes called grease ice, which eventually grows into small floes of pancake ice. If the lake is small enough or the weather cold enough, the floes may freeze together into a fairly solid sheet of pack ice. Pack ice may cover the entire lake or be restricted to areas near the shore.
3 Because water expands when it freezes, ice is less dense than liquid water and therefore floats rather than sinks in water.As ice floats on the surface of a lake, ocean, or river, it acts as an insulator and is thus important in maintaining the balance of the ecosystem. Without the insulating effect of floating ice sheets, surface water would lose heat more rapidly, and large bodies of water such as theArctic Ocean and HudsonBay might freeze up completely.
What condition is necessary for water in the atmosphere to change to its solid stateA、solid cloud cover that absorbs the sun’s heat
B．A、weather forecast for snow, sleet, or hail
C．A、position directly above a large body of water
D．A、temperature below water’s freezing point
网考网参考答案：D，答错率：44%
网考网试题解析：
Glues: Two conditions are necessary for the formation of ice: the presence of water and temperatures below freezing. Ice in the atmosphere...can assume various forms, depending on the conditions under which water is converted to its solid state.
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