托福阅读试题

word "proliferation" in the passage (paragraph 1) is closest in meaning to

1 supports which of the following statements about life on Earth before the Cambrian period?

levels were steady, as indicated by the fossil

of biodiversity could not be

most dramatic extinction episode

microscopic species

of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential

dominance of dinosaurs came to an end 65 million years ago, at which time mammals began to flourish and

no group of species can remain dominant forever, mammals became the dominant group when dinosaurs became

being the dominant group for more than 200 million years, the age of dinosaurs came to a dramatic end 65 million years

diverse group of mammals that we know today, including bats and whales, evolved from small terrestrial forms that had been dominated by

to paragraph 2, why are dinosaurs popularly said to have "ruled Earth" during the Cretaceous period?

were the only species of reptile that existed during the whole of the Cretaceous

won the battle for food resources over mammals during the Cretaceous

survived extinction during the Cretaceous period, whereas many other animal species did

were the physically and ecologically dominant animals during the Cretaceous

to paragraph 2, which of the following species initially increased in number at the K-T boundary?

does the author note that "even endotherms can be affected by a significant change in the climate"(paragraph 3)?

argue that there was a significant climate at the time that endothermic dinosaurs became

argue that climate change caused some dinosaurs to evolve as

support the view that at least some of the dinosaurs that became extinct were

defend climate change as possible explanation for the extinction of

word "generated"(paragraph 4) in the passage is closest in meaning to

word "extensive"(paragraph 4) in the passage is closest in meaning to

to paragraph 4, all of the following contributed to the massive extinctions of the K-T period EXCEPT:

solar

to paragraph 4, which of the following statements explains the importance of the discovery of high levels of iridium rocks?

provided evidence that overexposure to solar radiation led to the K-T

showed that more than one cataclysmic event was responsible for the K-T

suggested that the cause of the K-T extinction may have been a meteorite striking

provided evidence that the K-T extinction occurred 65 million years

to paragraph 4, which of the following is true about the Yucatan Peninsula?

circular formation there was caused by a meteorite impact 65 million years

rocks from that area have the lowest iridium concentration of any rocks on

is evidence that a huge tidal wave occurred there 65 million years

found there challenged the meteorite impact

of the following can be inferred from paragraph 4 about the meteorite theory?

data originally presented as evidence for the theory were eventually

scientists did not accept it when it was first

has not been widely accepted as an explanation for the K-T

subsequently revised it after a circular formation was found in the Yucatan

Look at the four squares [■] that indicate where the following sentence could be added to the Where would the sentence best fit? This focused on the chemical composition of ancient

Explanations for the K-T extinction were revolutionized in 1980 when a group of physical scientists led by Luis Alvarez proposed that 65 million years ago Earth was stuck by a 10-kilometer-wide meteorite traveling at 90,000 kilometers per They believed that this impact generated a thick cloud of dust that enveloped Earth, shutting out much of the incoming solar radiation and reducing plant photosynthesis to very low Short-term effects might have included huge tidal waves and extensive In other words, a series of events arising from a single cataclysmic event caused the massive ■【A】Initially, the meteorite theory was based on a single line of ■【B】At locations around the globe, geologists had found an unusually high concentration of iridium in the layer of sedimentary rocks that was formed about 65 million years ■【C】Iridium is an element that is usually uncommon near Earth's surface, but it is abundant in some ■【D】Therefore, Alvarez and his colleagues concluded that it was likely that the iridium in sedimentary rocks deposited at the K-T boundary had originated in a giant meteorite or Most scientist came to accept the meteorite theory after evidence came to light that a circular formation, 180 kilometers in diameter in diameter and centered on the north coast of the Yucatan Peninsula, was created by a meteorite impact about 65 million years

Prose Summary

The K-T extinction 65 million years ago is the best known of the five major extinction episodes since the Cambrian

, the five major extinction episodes resulted in the elimination of a larger number of species than did all the minor extinction

K-T extinction eliminated the dinosaurs and ammonoid mollusks but was followed by the diversification of mammals and gymnospermous

extreme cooling of the climate could not have caused the K-T extinction of dinosaurs, because, while most dinosaurs depended on environmental heat, some did

K-T extinction of the dinosaurs is the only mass extinction that has been explained by the impact of a

1980 Luis Alvarez proposed that the K-T extinction was caused by ecological disasters brought about by the impact of a meteorite striking

high concentration of iridium in sedimentary rocks at the K-T boundary and a large impact crater in the Yucatan Peninsula from 65 million years ago strongly support Alvarez'