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问题 单项选择题

已知220伏电压，40瓦灯泡，它的电阻是（）。

A.2300欧

B.3200欧

C.1210欧

D.620欧

答案

参考答案：C

单项选择题

女患者，29岁，停经46天， * * 少量出血5天，色淡红，右下腹隐痛，查尿妊娠试验阳性，B超检查宫腔内未见胎囊，诊断为异位妊娠未破损型，中药保守治疗的治法是：

A．活血化瘀，消癥杀胚

B．活血祛瘀，佐以益气

C．回阳救脱，活血祛瘀

D．破瘀消癜

E．理气活血，祛瘀消癥
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单项选择题

ICE


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 North America, 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.
3Because 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 the Arctic Ocean and Hudson Bay might freeze up completely.

Ice that forms in the atmosphere in the form of layered lumps is known as

A．snow

B．pack ice

C．hail

D．grease ice
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