Scientists discovered the genetic secret of the Black Death by

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问题 Scientists discovered the genetic secret of the Black Death by
News Item 2
    Scientists have reconstructed the entire genetic map of the germ that caused the Black Death, the bubonic plague that has killed millions in the 14th century.
    Humans have rarely encountered an enemy as devastating as the bacterium Yersinia pestis. Between 1347 and 1351, it sparked the Black Death, an infection carried by fleas that spread rapidly across Europe, killing around 50 million people. (3) Now scientists have uncovered some of the genetic secrets of the plague thanks to DNA fragments drilled from the teeth of victims buried in a graveyard in east London. The researchers say that all current strains circulating in the world are directly related to the medieval bacterium.

选项 A、unburying the victims from the graveyard.
B、studying the DNA fragments of the victims.
C、relating the current bacteria to the medieval ones.
D、reconstructing the map of the medieval England.

答案B

解析 根据句(3)可知,科学家们通过将在伦敦东部的墓穴安葬的黑死病患者的牙齿中钻出小的组织碎片,并研究其DNA构造,从而发现了引起黑死病病菌的基因秘密,故答案选[B]。
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