求问GWD3-Q7的B选项...

天使的旋律

GWD3-Q5 to Q7:

In 1994, a team of scientists led

by David Mckay began studying the
meteorite ALH84001, which had been
Linediscovered in Antarctica in 1984.
(5)Two years later, the McKay team
announced that ALH84001, which
scientists generally agree originated
on Mars, contained compelling evi-
dence that life once existed on Mars.
(10)This evidence includes the discovery
of organic molecules in ALH84001,
the first ever found in Martian rock.
Organic molecules—complex, carbon-

based compounds—form the basis for
(15)terrestrial life.The organic molecules
found in ALH84001 are polycyclic aro-
matic hydrocarbons, or PAH’s.When
microbes die, their organic material
often decays into PAH’s.
(20)Skepticism about the McKay team’s
claim remains, however.For example,
ALH84001 has been on earth for
13,000 years, suggesting to some
scientists that its PAH’s might have
(25)resulted form terrestrial contamination.
However, McKay’s team has demon-
strated that the concentration of PAH’s
increases as one looks deeper into
ALH84001, contrary to what one would
(30)expect from terrestrial contamination.
The skeptic’s strongest argument,
however, is that processes unrelated
to organic life can easily produce all
the evidence found by McKay’ steam,
(35)including PAH’s.For example, star
formation produces PAH’s.Moreover,
PAH’s frequently appear in other
meteorites, and no one attributes
their presence to life processes.
(40)Yet McKay’s team notes that the
particular combination of PAH’s
in ALH84001 is more similar to the
combinations produced by decaying
organisms than to those originating
form nonbiological processes.

--------------------------------------------------------------------------------
Q7:
The passage suggests that the fact that ALH84001 has been on earth for 13,000 years has been used by some scientists to support which of the following claims about ALH84001?

ALH84001 may not have originated on Mars.
ALH84001 contains PAH’s that are the result of nonbiological processes.
ALH84001 may not have contained PAH’s when it landed on Earth.
The organic molecules found in ALH84001 are not PAH’s.
The organic molecules found in ALH84001 could not be the result of terrestrial contamination.

划蓝线的部分对应此题...根据原句是说可能是地球的污染才造成了PAH的形成，也就是说在没着陆到地球之前没有污染可能就不会形成PAH...所以选C...已经理解...

问题是为什么B是不对的...看了以前的讨论，有两种说法，一下子想不通觉得都不能完全解释：
1. B选项是Mckay's team给出的...
2. B选项中说是nonbiological...文中说明的是biological的...

我对B选项的理解是：
显然Mckay's team认为是When microbes die, their organic material often decays into PAH’s"...这是一个biological process...
因为是地球污染才会让PAH形成...所以是有contamination这一nonbiological factor造成的...所以B选项也可能是对的...
（难道是选项说是仍然是biological process...只是nonbilogical factor起了作用？）

谢解答!

liuli_beryl

我觉得因为c更忠实原文，不需要任何进一步的推论，而b有一定的解释成分，并不能说明一定是Non-biological的流程。拙见供参考。请nn们来谈谈，真理会越辩越明的。顶顶顶！！！

天使的旋律

我觉得因为c更忠实原文，不需要任何进一步的推论，而b有一定的解释成分，并不能说明一定是Non-biological的流程。拙见供参考。请nn们来谈谈，真理会越辩越明的。顶顶顶！！！

-- by 会员 liuli_beryl (2010/8/12 22:50:07)

嗯...的确从推理的直接来讲...C比较直接...