【正文】 lopment of flowering plants caused dinosaurs to bee extinctC. To suggest that dinosaurs were able to survive for as long as they did because of the availability of flowering plantsD. To emphasize that duckbill dinosaurs and horned dinosaurs were the first dinosaurs to bee extinct2. The word “allegedly” in the passage is closest in meaning toA. inevitablyB. graduallyC. SupposedlyD. Increasingly3. According to paragraph 1 the extinction of the dinosaurs is unlikely to have been the result of petition from mammals becauseA. mammals would not have been capable of eating dinosaur eggsB. mammals did not appear in any significant numbers until after the Late TriassicC. mammals and dinosaurs did not, in fact, pete for any of the same resourcesD. mammals and dinosaurs lived together for roughly 120 million years before the extinctionparagraph 2This focus on explaining dinosaur extinction misses an important point the extinction at the end of the Cretaceous was a global event that killed off organisms up and down the food chain. It wiped out many kinds of plankton in the ocean and many marine organisms that lived on the plankton at the base of the food chain. These included a variety of clams and snails, and especially the ammonites, a group of shelled squidlike creatures that dominated the Mesozoic seas and had survived many previous mass extinctions. The KT event marked the end of the marine reptiles, such as the mosasaurs and the plesiosaurs, which were the largest creatures that had ever lived in the seas and which ruled the seas long before whales evolved. On land, there was also a crisis among the land plants, in addition to the disappearance of dinosaurs. So any event that can explain the destruction of the base of the food chain (plankton in the ocean, plants on land) can better explain what happened to organisms at the top of the food chain, such as the dinosaurs. By contrast, any explanation that focuses strictly on the dinosaurs pletely misses the point The Cretaceous extinctions were a global phenomenon, and dinosaurs were just a part of a bigger picture.paragraph 3According to one theory, the Age of Dinosaurs ended suddenly 65 million years ago when a giant rock from space plummeted to Earth. Estimated to be ten to fifteen kilometers in diameter, this bolide (either a et or an asteroid) was traveling at cosmic speeds of 2070 kilometers per second, or 45,000156,000 miles per hour. Such a huge mass traveling at such tremendous speeds carries an enormous amount of energy. When the bolide struck this energy was released and generated a huge shock wave that leveled everything for thousands of kilometers around the impact and caused most of the landscape to burst into flames. The bolide struck an area of the Yucatan Peninsula of Mexico known as Chicxulub, excavating a crater 1520 kilometers deep and at least 170 kilometers in diameter. The impact displaced huge volumes of seawater, causing much flood damage in the Caribbean. Meanwhile, the bolide itself excavated 100 cubic kilometers of rock and debris from the site, which rose to an altitude of 100 kilometers. Most of it fell back immediately, but some of it remained as dust in the atmosphere for months. This material, along with the smoke from the fires, shrouded Earth, creating a form of nuclear winter. According to puterized climate models, global temperatures fell to near the freezing point, photosynthesis halted, and most plants on land and in the sea died. With the bottom of the food chain destroyed, dinosaurs could not survive.4. According to paragraph 2, what is problematic about some scientists39。 antelope squirrels have which of the following in mon?A. They are the two smallest rodents now found in the southwestern United States.B. They have white coloring underneath their tailsC. They cannot cross the Grand CanyonD. They cannot survive in desert conditionsparagraph 4Geographic isolation creates opportunities for new species to develop, but it does not necessarily lead to new species because speciation occurs only when the gene pool undergoes enough changes to establish reproductive barriers between the isolated population and its parent population. The likelihood of allopatric speciation increases when a population is small as well as isolated, making it more likely than a large population to have its gene pool changed substantially. For example, in less than two million years, small populations of stray animals and plants from the South American mainland that managed to colonize the Galapagos Islands gave rise to all the species that now inhabit the islands. word “undergoes” in the passage is closest in meaning to 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 informationA. Geographic isolation is sometimes but not always the reason for the creation of reproductive barriers between a parent population and the populations descended from itB. Genetic changes in a geographical isolated population do not necessarily make the population look different enough from its parent population to be considered a new speciesC. Geographical isolation allows the separated populations to evolve independently of each other and so can lead to the formation of new speciesD. Geographic isolation can lead to new species only if the gene pool of the isolated population changes enough to prevent it from reproducing with the parent population to paragraph 4, why does the size of a population affect the likelihood of allopatric speciation?A. Because smaller populations are more likely than larger ones to bee geographically isolatedB. Because the gene pool of a small isolated population is more likely to undergo substantial change than is the gene pool of a larger populationC. Because a isolated population can bee a new species with substantially