求助 几道逻辑题

1 Grazing livestock on public land in the western United States is not causing widespread environmental damage in the region, since if it were,  the condition of that land would not be improving. However, only 14percent of public land in the are today is considered to have in adequate vegetation cover and, therefore, to be in poor condition, while in the 1930's, 36percent had in adequate vegetation cover.

which of the following , if true , most seriously weakens the argument above

A in the western united state, private land is typically more lush than public land, and cattle that graze on private land can be fattened more quickly.

Bsince the 1930's,recreational users of public land in the western united states have caused more environmental damage than have the cattle grazing there.

C during the 1930's , an unusually destructive drought prevailed throughout the region where most public lands in the western united states are located.

D Ranchers who use public land in the western united states pay only a fraction of what is paid by those who lease comparable private land for grazing

E the amount of land purchase by the united states government since the 1930's is relatively insignificant.

答案是C 让我非常想不明白

2 The large amount of carbon dioxide now being released into the atmosphere bu the buring of fossil fuels will not, in fact, result in a greenhouse effectan increase in average global temperatures. since plants use dioxide in lager quantities if the supply  is increased, they are able to grow larger and multiply more vigorously, and atmospheric carbon dioxide concentrations will eventually become stable.

which of the following, if true , would most seriously weaken the conclusion that a greenhouse effect will not result from the current release of large amounts of carbon dioxide into the atmosphere?

Athe expected rise in average global temperature has not yet been observed.

B Ocean water obsorb carbon dioxide at a greaer rate when the atmosphere concentration of carbon dioxide is higher.

C since the beginning of the Industrial revolution, increased atmospheric concentratons of carbon dioxide have resulted in improved agriculture productivity.

D when plants decay, they produce methane, another gas that can have a marked greenhouse effect.

E 就不打了 没意义的一个选项

答案是选D 但我觉得B比较对啊 D说的是METHANE  题目说的是CARBON DIOXIDE

5 The ration of divorces to marriages has increased since 1940. Therefore, there must be a greater proportion of children living with only one natural parent than there was in 1940.

Which of the following if true, most strongly weakens the inference drawn above.

A the number of marriages entered into by women twentyfibe to 30ys old has decreased since1940/

b when there is a divorce, children are often given the option of deciding which parent they will live with.

C since 1940 the average number of children in a family has remaned approximately steady and has not been subject to wide fluctuations.

D before 1940 relatively few children whose parents had both died were adoptedin to single-parent families.

Ethe proportion of children who must be raised by one parent because the other had died has decreased since 1940 as a result of medical advances.

答案选E 但我怎么觉得E是加强呢。。。。

谢谢大家帮我解答

第一题的c选项表现的是一个特例，所以1936年的植被覆盖少不能用来证明目前的植被是不受侵害的，所以削弱题干中的观点。

第三题中说因为离婚率上升所以单亲家庭的小孩会增多，只要选项中能反驳这个观点的就是正确答案，e说明随着医疗的进步，家庭中双亲的死亡率下降，所以单亲现象减少，所以对。

第二题的b是无关项，大海吸收更多CO2不能说明问题，但是D也看不出哪里对

顶顶～