問題詳情

Questions 1-8Prehistoric mammoths have been preserved in the famous tar pits of Rancho La Brea(Brea is the Spanish word for tar) in what now the heart of Los Angeles, California.These tar pits have been known for centuries and were formerly mined for their naturalLine asphalt, a black or brown petroleum-like substance. Thousands of tons were extracted(5) before 1875, when undertaken that established the significance of this remarkable site.excavations were undertaken that established the significance of this remarkable siteThe tar pits were found to contain the remains of scores of species of animals from the last30,000 years of the Ice Age.Since then, over 100 tons of fossils, 1.5 million from vertebrates, 2.5 million from(10) invertebrates, have been recovered, often in densely concentrated tangled masses. Thecreatures found range form insects and birds to giant ground sloth’s, but a total of 17proboscides (animal with a proboscis or long nose)- including mastodons andColumbian mammoths- have been recovered, most of them from Pit 9, the deepestbone-bearing deposit, which was excavated in 1914. Most of the fossils date to between(15) 40,000 and 10,000 years ago.The asphalt at La Brea seeps to the surface, especially in the summer, and formsshallow puddles that would often have been concealed by leaves and dust. Unwaryanimals would become trapped on these thin sheets of liquid asphalt, which are extremelysticky in warm weather. Stuck, the unfortunate beasts would die of exhaustion and(20) hunger or fall prey to predators that often also became stuck.As the animals decayed, more scavengers would be attracted and caught in their turn.Carnivores greatly outnumber herbivores in the collection: for every large herbivore,there is one saber-tooth cat, a coyote, and four wolves. The fact that some bones areheavily weathered shows that some bodies remained above the surface for weeks or(25) months. Bacteria in the asphalt would have consumed some of the tissues other thanbones, and the asphalt itself would dissolve what was left, at the same time impregnatingand beautifully preserving the saturated bones, rendering then dark brown and shiny.
1.What aspect of the La Brea tar pits does thepassage mainly discuss?
(A)The amount of asphalt that was mined there
(B) The chemical and biological interactionsbetween asphalt and animals
(C) The fossil remains that have been foundthere
(D) Scientific methods of determining the ageof tar pits

參考答案

答案：C
難度：困難0.2
統計：A(2),B(2),C(1),D(0),E(0)

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