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  3. Conventional wisdom has long held that mammals stayed millions of years on earth. As long as dinosaurs roamed the lands, our dis

Conventional wisdom has long held that mammals stayed millions of years on earth. As long as dinosaurs roamed the lands, our dis

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问题     Conventional wisdom has long held that mammals stayed millions of years on earth. As long as dinosaurs roamed the lands, our distant ancestors never got to be much more than chicken-hearted creatures that sneaked out at night to grab bits of plants when the terrible lizards were asleep. Only when they were wiped out did mammals begin to earn a little evolutionary respect.
    But that picture changed dramatically with the announcement in Nature of two impressive fossils. One, of a brand-new species named R. giganticus, broke apart the notion that most dinosaur-age mammals were never larger than squirrels. The animal had the dimensions of a midsize dog-by far the biggest dinosaur-age mammal ever found. And the second, a new specimen of a previously discovered species called R. robustus, refuted the notion that it was always the mammals that got eaten. Inside the skeleton where the animal’s stomach would have been are the fossilized remains of a baby dinosaur. " This discovery was the chance of a lifetime, " says Jin Meng, scientist and coauthor of the paper.
    Indeed, Meng didn’t expect to find things like this at all. The smaller skeleton was discovered about two years ago by villagers in China’s Liaoning province, site of some of the richest fossil beds in the world. They brought it to the attention of scientists, who took it to an institute for examination. "We didn’t see the stomach contents at first, " says Meng.
    After they did, however, it didn’t take them long to realize they had struck scientific gold. On closer examination, the scientists determined that the remains were those of a juvenile dinosaur. Some of the arm and leg bones were still attached to each other, suggesting that R. robustus didn’t chew its food thoroughly but wolfed it down in large chunks.
    Taken together, the finds overturn the already eroded idea that early mammals were tiny and timid. Now paleontologists can stop cooking up theories to explain why mammals were so little— that they had to be small to avoid being found, for example, or they couldn’t grow larger because dinosaurs already occupied those ecological spaces.
    But it’s now clear that mammals did fill some of the spaces reserved for larger animals. "It’s quite possible, " says paleontologist Anne Weil, " that they competed with dinosaurs for the same prey. " And because they ate dinosaurs, they may even have had an influence on dinosaur evolution. What sort of influence? "We don’t know, " she says. "That’s how it is with the best finds. They leave you with more questions than answers. "
By saying "they had struck scientific gold" (Lines 1—2, Paragraph 4), the author means that
选项 A、their discovery earned them great fame.
B、their findings enjoyed enormous market value.
C、they acquired valuable resources for their studies.
D、they had made a significant discovery in their research.
答案D
解析 句意：“they had struck scientific gold”(第四段第1-2行)是什么意思?根据第二段最后一句“‘This discovery was the chance of a lifetime，’says Jin Meng，scientist and co-author of the paper．”可知，在哺乳动物胃部发现恐龙遗骸这一发现是千载难逢的。因此，“struck scientific gold”意为他们在研究领域内作出了重大发现，故选D。
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