A. which B. than C. to Phrases: A.【T7】___________cany poisonous substances B. more【T8】___________2,600 square kil

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问题 A. which
B. than
C. to
     Phrases:
     A.【T7】___________cany poisonous substances
     B. more【T8】___________2,600 square kilometers
     C. These nutrients can contribute【T9】___________the breeding of the organisms
     The term "red tide" applies to the discoloration of water that sometimes occurs in certain areas of the ocean or sea . Although the color is often red , it may also be shades of brown or yellow. The World Book Encyclopedia reports that " the discolored areas may range from less than a few square yards to【T10】_______________"
     What causes such discoloration? Red tides are generally caused by several species of single-celled organisms. These tiny organisms have hair-like projections which they use to propel themselves in water.
     There are about 2,000 varieties of these organisms, 30 of【T11】______________. These minute organisms usually stay in warm waters with high content of salt.
     A red tide occurs when there is a sudden and rapid bloom of these organisms. The concentration of these organisms may swell to 50, 000,000 per quart of water! Although scientists do not fully understand why this happens, it is known that these organisms accumulate when certain conditions simultaneously affect the water. These include abnormal weather, optimum temperatures, an oversupply of nutrients in the water, a generous amount of sunlight, and favorable water currents. When a heavy rainfall occurs, minerals and other nutrients are sometimes washed from the land into coastal water.【T12】______________. The result? Red tides!
【T12】

选项 A、 
B、 
C、 

答案C

解析 空格前一句表达的意思为:当出现暴雨时,矿物质和其他营养物有时被从陆地冲向沿海水域。结合空格后的描述可知C项“这些营养物可能促进这些微生物的生长”符合上下文。
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