老prepCR题求助！

candyloun

1.    (24179-!-item-!-188;#058&000705)

Although fullerenes--spherical molecules madeentirely of carbon--were first found in the laboratory, they have since beenfound in nature, formed in fissures of the rare mineral shungite.  Since laboratory synthesis of fullerenesrequires distinctive conditions of temperature and pressure, this discoveryshould give geologists a test case for evaluating hypotheses about the state ofthe Earth's crust at the time these naturally occurring fullerenes were formed.

Which of the following, if true, most seriouslyundermines the argument?

(A) Confirming that the shungite genuinelycontained fullerenes took careful experimentation.

(B) Some fullerenes have also been found on theremains of a small meteorite that collided with a spacecraft.

(C) The mineral shungite itself contains largeamounts of carbon, from which the fullerenes apparently formed.

(D) The naturally occurring fullerenes arearranged in a previously unknown crystalline structure.

(E) Shungite itself is formed only underdistinctive conditions.

答案给的是D  哪位大虾能帮我讲解一下为什么选这个来

candyloun

2.    (24227-!-item-!-188;#058&000711)

Economist:  On average, the emergency treatment for an elderly person for injuries resulting from a fall costs $11,000.  A new therapeutic program can significantly reduce an elderly person's chances of falling.  Though obviously desirable for many reasons, this treatment program will cost $12,500 and thus cannot be justified.

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

(A) Among elderly people who had followed the program for only a few months, the number of serious falls reported was higher than it was for people who had followed the program for its recommended minimum length of one year.
(B) Falls resulting in serious injuries are less common among elderly people living in nursing homes than they are among elderly people who live alone at home.
(C) A frequent result of injuries sustained in falls is long-term pain, medication for which is not counted among the average per-person costs of emergency treatment for elderly people's injuries from such falls.
(D) The new therapeutic program focuses on therapies other than medication, since overmedication can cause disorientation and hence increase the likelihood that an elderly person will have a serious fall.
(E) A significant portion of the cost of the new therapeutic program is represented by regular visits by health care professionals, the costs of which tend to increase more rapidly than do those of other elements of the program.

还有这个题 答案是C  为什么不选D呢

candyloun

(27669-!-item-!-188;#058&003302)

Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas.  In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide.  lants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?

(A) The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
(B) At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
(C) The urban class conducting the experiment was larger than the rural class conducting the experiment.
(D) Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.
(E) Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.


还有这个题为什么选D

tinycotton

看这个帖
http://forum.chasedream.com/GMAT_CR/thread-502310-1-1.html?postid=14548000&searchmode=TopicContent&searchtext=24179%20item%20188%20058%2000070我自己的理解是这是个类比型的WEAKEN题， D说明了比较两者本质不同。naturally occurring fullerenes has different structure from synthesized fullerenes， 所以基于这个假设上面的比较也是不正确的。
这些题目搜下CD基本都有讨论帖