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  3. There have long been dead zones–water too low in oxygen to sustain most forms of life—in the Gulf of Mexico, which receives the

There have long been dead zones–water too low in oxygen to sustain most forms of life—in the Gulf of Mexico, which receives the

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问题 There have long been dead zones–water too low in oxygen to sustain most forms of life—in the Gulf of Mexico, which receives the waters of the Mississippi River. Scientists studied sediment cores from areas where the gulf’s most recent dead zone occurred. The scientists dated the sediment and counted species of foraminifera (marine protozoans) in the sediment; these species thrive in low-oxygen waters. As far back as 1823, the foraminifera thrived especially during Mississippi River flood years (during which nutrients levels increase), suggesting that nutrients in floodwaters can trigger low-oxygen water. The foraminifera in the core samples were most abundant after 1950, when farmers began using some fertilizer, which is rich in nutrients. Researchers believe that increased use of fertilizer leads to more-extreme dead zones.
It can be inferred from the passage that the “researchers” would agree with which of the following statements about the use of fertilizer?
选项 A、If farmers near the Mississippi River decreased the amount of fertilizer that they used, the severity of the dead zones could be diminished.
B、If farmers near the Mississippi River continue their dependence upon fertilizers, foraminifera population will eventually decline.
C、If farmers near the Mississippi River stopped using fertilizers altogether, there would no longer be dead zones.
答案A
解析 文章最后研究者们得到的结论就是肥料的增加会促进死亡区域的产生。因此，肥料的减少也必然会减少死亡区域的产生。A正确。
本文只能看出，继续使用肥料，死亡区域会一直存在，因而foraminifera会一直生长。至于以后foraminifera会不会减少，文中看不出。B不选。
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