GWD 3-7 想再问一下下

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?

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

B 中的nonbiological processes 怎么理解？terrestrial contamination 难道不是可以说是一种nonbiological processes？ 求教

I chose C.  

Terrestrial contamination may or may not be nonbiological processes. "ALH84001 may not have contained PAH’s when it landed on Earth" as stated in choice C, but it is later contaminated by microbes which died on earth.