2. 考研
  3. Even ancient Egypt’s mighty pyramid (金字塔) builders were powerless in the face of the famine (饥荒) that helped bring down their ci

Even ancient Egypt’s mighty pyramid (金字塔) builders were powerless in the face of the famine (饥荒) that helped bring down their ci

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问题     Even ancient Egypt’s mighty pyramid (金字塔) builders were powerless in the face of the famine (饥荒) that helped bring down their civilization around 2180 B. C. Now evidence collected from mud deposited by the River Nile suggests that a shift in climate thousands of kilometers to the south was ultimately to blame—- and the same or worse could happen today.
    The ancient Egyptians depended on the Nile’s annual floods to irrigate their crops. But any change in climate that pushed the African monsoons (季风) southwards out of Ethiopia would have reduced these floods.
    Declining rains in the Ethiopian highlands would have meant fewer plants to stabilize the soil. When rain did fall it would have washed large amounts of soil into the Blue Nile and into Egypt, along with sediment (沉积) from the White Nile.
    Blue Nile mud has a different isotope (同位素) signature from that of the white Nile. So by analyzing isotope differences in mud deposited in the Nile Delta. Michael Krom of Leeds University worked out what proportion of sediment came from each branch of the river.
    Krom reasons that during periods of drought, the amount of Blue Nile mud in the river would be relatively high. He found that one of these periods, from 4500 to 4200 years ago. immediately came before the fall of the Egypt’s old Kingdom.
    The weakened waters would have been disaster for the Egyptians. "Changes that affect food supply don’t have to be very large to have a ripple (波浪) effect in societies," says Bill Ryan of the Lamont Doherty Earth Observatory in New York.
    Similar events today could be even more devastating, says team member Daniel Stanley. A scientist from the Smithsonian Institution in Washington D. C. "Anything humans do to shift the climate belts would have an even worse effect along the Nile system today because the populations have increased dramatically."  
Which of the following statements is true?
选项 A、The White Nile is the trunk of the River Nile.
B、The White Nile is the trunk of the Blue Nile.
C、The White Nile is a branch of the Blue Nile.
D、The White Nile is a branch of the River Nile.
答案D
解析 第四段最后一句：…worked out what proportion of sediment came from each branchof the river．……找到了来自河的每条支流的沉积物的比例。这里的“河”是指“尼罗河”，“每条支流”指上文所说的“青尼罗河”和“白尼罗河”。故答案为D。
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