Q5 to Q7:
In 1994, a team of scientists led
by David Mckay began studying the
meteorite ALH84001, which had been
Line discovered in
(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 from 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?
Answer: C
实在想不通，文章里面很清楚找出是E阿
搜索出来, GWD 12 的5-7题居然和我的文章不一样，太奇怪了
请大家帮忙看一下，谢谢！
Line 22 of the passage states:
"ALH84001 has been on earth for 13,000 years, suggesting to some scientists that its PAH’s might have resulted from terrestrial contamination."
If PAH has resulted from terrestrial contamination, then most likely it did not originate from Mars, that is, when the meteorite landed on Earth it did not contain PAH. Therefore, C is correct.
E directly contradicts line 22's statement by asserting that the organic molecules found in the meteorite could NOT have resulted from terrestrial contamination; therefore it is incorrect.
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