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【单选题】

第三篇
There are some earth phenomena you can count on, but the magnetic field, some say, is not one of them. It fluctuates in strength, drifts from its axis, and every few 100,000 years undergoes a dramatic polarity reversal —a period when north pole becomes south pole and south pole becomes north pole. But how is the field generated, and why is it so unstable
Groundbreaking research by two French geophysicists promises to shed some light on the mystery. Using 80 metres of deep sea sediment (沉淀物) core, they have obtained measurements of magnetic-field intensity that span 11 polarity reversals and four million years. The ysis reveals that intensity appears to fluctuate with a clear, well-defined rhythm. Although the strength of the magnetic field varies irregularly during the short tern, there seems to be an inevitable long-term decline preceding each polarity reversal. When the poles flip—a process that takes several hundred thousand years--the magnetic field rapidly regains its strength and the cycle is repeated.
The results have caused a stir among geophysicists. The magnetic field is thought to originate from molten (熔化的) iron in the outer core, 3,000 kilometers beneath the earth’s suce. By studying mineral grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730,000 years age. How and why they occur, however, has been widely debated. Several theories link polarity flips to external disasters such as meteor (陨星) impacts. But Peter Olson, a geophysicist at the Johns Hopkins University in Baltimore, says this is unlikely if the French researchers are right. In fact, Olson says intensity that predictably declines from one reversal to the nest contradicts 90 percent of the models currently under study. If the results prove to be valid geophysicists will have a new theory to guide them in their quest to understand the earth’s inner physics. It certainly points the direction for future research.
The French geophysicists’ study is different from currently prevailing theories in______.

A.
its identification of the origin of the earth’s magnetic field
B.
the way the earth’s magnetic intensity is measured
C.
its explanation of the shift in the earth’s polarity
D.
the way the earth’s fluctuation rhythm is defined
题目标签:沉淀物熔化陨星
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【单选题】脑脊液沉淀物涂片发现白血病细胞______

A.
梅毒性脑炎
B.
结核性脑膜炎
C.
病毒性脑膜炎
D.
真菌性脑膜炎
E.
脑膜白血病

【单选题】下列关于沉淀物的来源正确的是( )

A.
泪液成分中的蛋白质
B.
泪液中的脂质
C.
化妆品
D.
细菌
E.
以上全部正确

【单选题】SCL蛋白质沉淀物的表现是()。

A.
灰绿色团块状物
B.
不均匀灰白色模糊斑片
C.
凝聚的胶质斑块
D.
灰白色硬质斑点

【单选题】冷沉淀物中不包含的凝血因子是()。

A.
因子Ⅷ
B.
因子Ⅸ
C.
因子Ⅻ
D.
vonWillebrand因子
E.
纤维蛋白原