标题: FEIFEI 81 [打印本页] 作者: ruirui_hsu 时间: 2011-7-19 18:35 标题: FEIFEI 81 81. Nuclear fusion is a process whereby the nuclei of atoms are joined, or “fused”, and in which energy is released. One of the by-products of fusion is helium-4 gas. A recent fusion experiment was conducted using “heavy” water contained in a sealed flask. The flask was, in turn, contained in an air-filled chamber designed to eliminate extraneous vibration. After the experiment, a measurable amount of helium-4 gas was found in the air of the chamber. The experiments cited this evidence in support of their conclusion that fusion had been achieved.
Which one of the following, if true, would cast doubt on the experimenters’ conclusion?
A.Helium-4 was not the only gas founding the experiment chamber.
B.When fusion is achieved, it normally produces several by-products, including tritium and gamma rays.
C.The amount of helium-4 found in the chamber’s air did not exceed the amount of helium-4 that is found in ordinary air.
D.Helium-4 gas rapidly breaks down, forming ordinary helium gas after a few hours.
E.Nuclear fusion reactions are characterized by the release of large amount of heat.
D.无关，本句中心是helium gas 不是h-4。Helium 属于文中没用提的东东，虽然都是helium.
E.无关，陷阱。试验中完全可能有大量的热，作者没用说，谁也不知道有没有热。
C说H4本来就有？可是原文中也没提到啊。就是说fusion产生了measuable amoung of H-4, 也没说本来就有啊？？？？ 作者: sdcar2010 时间: 2011-7-19 21:31
Typo: A.Helium-4 was not the only gas founding the experiment chamber.
should be: A.Helium-4 was not the only gas found in the experiment chamber.
This is a weaken question, which allows new information gleaned from the answer choice. C) is the right answer. Given the new info from C), one can conclude that no EXTRA H-4 has been produced after the "fusion" experiment.作者: fanaf821 时间: 2011-7-23 10:03
原文逻辑链 helium-4 found in the air of the chamber ==》 fusion had been achieved accoding to e, nuclear fusion reactions are characterized by the release of large amount of heat e选项仅仅说明实验的特征——放出大量热，无论它放不放热，都与我们要weaken的argument无关，即对fusion是否achieve没有影响，e选项成为正确选项需要原文更多的信息支持，它不是排除它因 也可以这么来看，排除他因即对argument 原因唯一性的削弱，argument 的原因是气体的发现，比较后不难发现e选项和argument的原因在说两回事