Q5 to Q7:
In 1994, a team of scientists led
by David Mckay began studying the
meteorite ALH84001, which had been
Line discovered 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.
- E .The organic molecules found in ALH84001 could not be the result of terrestrial contamination.
答案是c，我怎么觉得b对阿，见文中“
suggesting to some
scientists that its PAH’s might have
(25) resulted form terrestrial contamination.” | 
