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1、最新题 24 套124-1 Tom Bradley was mayor of Los Angeles from 1973 to 1993, an era when the city had transformed from a collection of suburban neighborhoods to the second-largest city in the United States. (A) an era when the city had transformed (B) an era during which the city was transformed (C) an era
2、 that transformed it (D) during which era the city transformed (E) during which the city was transformed24-Passage oneMore selective than most chemical pesticides in that they ordinarily destroy only unwanted species, biocontrol agents (such as insects, fungi, and viruses) eat, infect, or parasitize
3、 targeted plant or animal pests. However, biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources: a biocontrol agent might reduce the benefits conferred by a desirable animal species by consuming a plant on which the animal prefers to lay its egg
4、s. (Line 14)Another example of indirect negative consequences occurred in England when a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue bu
5、tterfly that had depended on the nests to shelter its offspring. The paucity of known extinctions of disruptions resulting from indirect interactions may reflect not the infrequency of such mishaps but rather the failure to look for or to detect them: most organisms likely to be adversely affected b
6、y indirect interactions are of little or no known commercial value and the events linking a biocontrol agent with an adverse effect are often unclear. Moreover, determining the potential (35) risks of biocontrol agents before they are used is difficult, especially when a nonnative agent is introduce
7、d, because, unlike a chemical pesticide, a biocontrol agent may adapt in unpredictable ways, so that it can feed on or otherwise harm new hosts.24-3 The passage is primarily concerned with (A) explaining why until recently scientists failed to recognize the risks presented by biocontrol agents. (B)
8、emphasizing that biocontrol agents and chemical pesticides have more similarities than differences. (C) suggesting that only certain biocontrol agents should be used to control plant or animal pasts. (D) arguing that biocontrol agents involve risks, some of which may not be readily discerned. (E) su
9、ggesting that mishaps involving biocontrol agents are relatively commonplace.24-4 The passage suggests that the author would be most likely to agree with which of the following statements about the use of biocontrol agents? (A) Biocontrol agent should be used only in cases where chemical pesticides
10、have proven ineffective or overly dangerous. (B) Extinctions and disruptions resulting from the use of biocontrol agents are likely to have increasingly severe commercial consequences. (C) The use of biocontrol agents does not require regulation as stringent as that required by the use of chemical p
11、esticides. (D) The use of biocontrol agents may even finally supersede the use of chemical pesticides in controlling unwanted species. (E) The risks of using native biocontrol agents may be easier to predict than the risks of using nonnative biocontrol agents.24-5 Which of the following is mentioned
12、 in the passage as an indirect effect of using a biocontrol agent? (A) Reduction of the commercial value of a desirable animal species (B) An unintended proliferation of a nontarget animal species (C) An unforeseen mutation in a target species (D) Diminution of the positive effects conferred by a no
13、ntarget animal species (E) Competition for resources with a largest species24-6 The example presented by the author in lines 14-23 most clearly serves to illustrate (A) a situation in which a species is less vulnerable to biocontrol agents than it would have been to chemical pesticides. (B) a way in
14、 which the introduction of a biocontrol agent can affect a nontarget species. (C) a nonnative agents adapting in an unpredictable way that results in damage to a new host. (D) the contention that biocontrol agents can harm nontarget species by competing with them for resources. (E) the way in which
15、indirect consequences from the use of biocontrol agents are most likely to occurs.24-7 Which of the following most logically completes the argument below?The expansion of large-scale farming in Africa and Asia has destroyed much of the natural vegetation on which elephants have historically depended
16、, forcing them to turn to cultivated land to satisfy their enormous appetites. As a result, farmers have lost millions of dollars worth of crops annually. Yet even if elephant sanctuaries were created on a widespread basis to guarantee elephants sufficient natural vegetation, the raiding would likely persist, since (A) when elephants forage for food, they typically travel in herds. (B) foraging elephants have been known to cause su
