Q5 to Q7:

In 1994, a team of scientists led

by David Mckay began studying the

meteorite ALH84001, which had been

Line discovered in LACE>AntarcticaLACE> 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.

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Q5:E

The passage asserts which of the following about the claim that ALH84001 originated on Mars?

1. It was initially proposed by the McKay team of scientists.
2. It is not a matter of widespread scientific dispute.
3. It has been questioned by some skeptics of the McKay team’s work.
4. It has been undermined by recent work on PAH’s.
5. It is incompatible with the face that ALH84001 has been on Earth for 13,000 years.

KEY: B, 为什么D不对？谢谢