几道GWD逻辑题的答案，想不通为什么，请高人讲解一下。

guoguotoronto

各位高人，这几道题我想不明白为什么选这个答案，可以帮忙讲解一下吗，谢谢了。











Q14:B

Plantings of cotton bioengineered to produce its own insecticide against bollworms, a major cause of crop failure, sustained little bollworm damage until this year.  This year the plantings are being seriously damaged by bollworms.  Bollworms, however, are not necessarily developing resistance to the cotton’s insecticide.  Bollworms breed on corn, and last year more corn than usual was planted throughout cotton-growing regions.  So it is likely that the cotton is simply being overwhelmed by corn-bred bollworms.



In evaluating the argument, which of the following would it be most useful to establish?

1. Whether corn could be bioengineered to produce the insecticide
   
2. Whether plantings of cotton that does not produce the insecticide are suffering unusually extensive damage from bollworms this year
   
3. Whether other crops that have been bioengineered to produce their own insecticide successfully resist the pests against which the insecticide was to protect them
   
4. Whether plantings of bioengineered cotton are frequently damaged by insect pests other than bollworms
   
5. Whether there are insecticides that can be used against bollworms that have developed resistance to the insecticide produced by the bioengineered cotton
   

Q11:B

Some species of Arctic birds are threatened by recent sharp increases in the population of snow geese, which breed in the Arctic and are displacing birds of less vigorous species.  Although snow geese are a popular quarry for hunters in the southern regions where they winter, the hunting season ends if and when hunting has reduced the population by five percent, according to official estimates.  Clearly, dropping this restriction would allow the other species to recover.





Which of the following, if true, most seriously undermines the argument?

1. Hunting limits for snow geese were imposed many years ago in response to a sharp decline in the population of snow geese.
   
2. It has been many years since the restriction led to the hunting season for snow geese being closed earlier than the scheduled date.
   
3. The number of snow geese taken by hunters each year has grown every year for several years.
   
4. As their population has increased, snow geese have recolonized wintering grounds that they had not used for several seasons.
   
5. In the snow goose’s winter habitats, the goose faces no significant natural predation.
   

Q38:E

Outbreaks of Rift Valley fever occur irregularly in East Africa, several years apart.  When outbreaks do occur, they kill thousands of cattle.  A livestock vaccine against the disease exists but is rarely used.  It is too expensive for farmers to use routinely, and since it is not effective until a month after vaccination, administering it after an outbreak begins helps very little.  Nevertheless, experts predict that use of the vaccine will increase significantly within the next few years.



Which of the following, if true, provides the strongest justification for the experts’ prediction?

1. Rift Valley fever is spread by mosquitoes, but each outbreak is so widespread that it is impractical to control it by using insecticides.
   
2. When an outbreak of Rift Valley fever occurs, unaffected countries often refuse to import livestock from the countries affected by the outbreak.
   
3. It would take less than a month for producers of the vaccine to adjust their production operations to cope with a large increase in demand.
   
4. Many cattle farmers in East Africa are nomadic or live in remote villages, and such farmers, who have little access to modern veterinary medicine, are particularly hard hit by outbreaks of Rift Valley fever.
   

Recently published research has shown that certain identifiable climatic conditions are almost invariably followed, within two to five months, by an outbreak of Rift Valley fever.






Q4

In the year following an eight-cent increase in the federal tax on a pack of cigarettes, sales of cigarettes fell ten percent.  In contrast, in the year prior to the tax increase, sales had fallen one percent.  The volume of cigarette sales is therefore strongly related to the after-tax price of a pack of cigarettes.



The argument above requires which of following assumptions?

1. During the year following the tax increase, the pretax price of a pack of cigarettes did not increase by as much as it had during the year prior to the tax increase.
   
2. The one percent fall in cigarette sales in the year prior to tax increase was due to a smaller tax increase.
   
3. The pretax price of a pack of cigarettes gradually decreased throughout the year before and the year after the tax increase.
   
4. For the year following the tax increase, the pretax price of a pack of cigarettes was not eight or more cents lower than it had been the previous year.
   
5. As the after-tax price of a pack of cigarettes rises, the pretax price also rises.