GWD 3-5

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.

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Q5:E      

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

It was initially proposed by the McKay team of scientists.

It is not a matter of widespread scientific dispute.

It has been questioned by some skeptics of the McKay team’s work.

It has been undermined by recent work on PAH’s.

It is incompatible with the face that ALH84001 has been on Earth for 13,000 years.

KEY: B, 为什么D不对那? 请教

announced that ALH84001, which

scientists generally agree originated

on Mars,

Q:about the claim that ALH84001 originated on Mars

A:It is not a matter of widespread scientific dispute.

mm没有看清题目吧。文章没有说PAH证明ALH84001并不是来自MARS.

GWD-3-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?

1. ALH84001 may not have originated on Mars.

2. ALH84001 contains PAH’s that are the result of nonbiological processes.

3. ALH84001 may not have contained PAH’s when it landed on Earth.

4. The organic molecules found in ALH84001 are not PAH’s.

5. The organic molecules found in ALH84001 could not be the result of terrestrial contamination.

答案是C，为什么呢？

GWD-3-7 ,我选择的是B.答案是C，我也觉得很难从文中很直接推导出来。反而B,那些scientist认为PAH不是microbs decay来的，而是contamination来的，正是B说的啊。

谁可以解答解答啊？

我也是选B的。好像在文中可以推出来啊。但是我推不出C

       ALH84001 has been on earth for

13,000 years, suggesting to some

scientists that its PAH’s might have

(25)      resulted form terrestrial contamination.

这里说A在地球上13000年，表明PAH可能是从地球上带来的。C是直接改写。

mms选B是因为定位错误。这里的13000年与下面的没有关系。这段作者说了两个怀疑：一是A在地球上已经13000年，二是31行开始，说PAH很容易找到。