Critical Reasoning

Commentator: Many people argue that the release of
chlorofluorocarbons into the atmosphere is
harming humans by damaging the ozone layer,
thus allowing increased amounts of ultraviolet
radiation to reach Earth. But 300,000 years ago a
supernova greatly damaged the ozone layer, with
no significant effect on our earliest ancestors.
Because the supernova’s disruption was much
greater than the estimated effect of
chlorofluorocarbons today, there is no reason to
think that these chemicals in the atmosphere
harm humans in this way.
Which one of the following, if true, would most
seriously weaken the commentator’s argument?
(A) Extraterrestrial influences on the ozone layer
tend to occur less often than terrestrial ones.
(B) Natural events, such as the eruption of
volcanoes, continue to damage the ozone layer
today.
(C) Our earliest ancestors possessed genetic
characteristics making them more resistant than
we are to the harmful effects of ultraviolet
radiation.
(D) The ozone layer regenerates at a slow rate,
barring counteractive processes.
(E) Scientists have discovered that genetic changes
occurred in our ancestors during the period in
which the supernova affected Earth.

I need a break....uff not able to get it right..... :roll:

Between A and C.I would go wih C.

Is it C?

Greater damage to the ozone layer did not affect our ancestors, so the damage caused to the ozone layer because of the relatively lesser CFCs are not going to affect humans.

By establishing that our ancestors possessed some special ability which helped them withstand the radiation,(which we now lack), the argument can be weakened.

it has to be C

OA is B
dnt know how...

B is reasonable, because the supernova actually did damage ozone layer but at a moderate rate that did not harm our ancestors, but since then natural events have continued to damage ozone layer more and more.
This weakens the arguement that the chemicals don't harm human at all.

However, I don't see any wrong with C and E.
Could anyone explain?

Spring2009 wrote:B is reasonable, because the supernova actually did damage ozone layer but at a moderate rate that did not harm our ancestors, but since then natural events have continued to damage ozone layer more and more.
This weakens the arguement that the chemicals don't harm human at all.

However, I don't see any wrong with B and E.
Could anyone explain?

Please give me reasoning to negate C

ankit1383 wrote:

Spring2009 wrote:B is reasonable, because the supernova actually did damage ozone layer but at a moderate rate that did not harm our ancestors, but since then natural events have continued to damage ozone layer more and more.
This weakens the arguement that the chemicals don't harm human at all.

However, I don't see any wrong with B and E.
Could anyone explain?

Please give me reasoning to negate C

Sorry I did typo, I also don't see anything wrong with C.
Also need an explaination.

But it is nowhere mentioned that the supernova caused moderate damage. Infact it says that the 'supernova greatly damaged the ozone layer'

Initially I also answered the question as C but later a thorough analysis provided the below explanation. Have a look and let me know if this makes sense

premise 1 - release of
chlorofluorocarbons into the atmosphere is
harming humans by damaging the ozone layer

premise 2 - supernova's disruption was much
greater than the estimated effect of
chlorofluorocarbons today

conclusion - there is no reason to
think that these chemicals in the atmosphere
harm humans in this way.

B)Natural events, such as the eruption of
volcanoes, continue to damage the ozone layer
today.

B explains that even though premise 2 is right, the danger is more, as there is one more source to damage the ozone layer (which might factor in the higher percentage and hence more danger)

Ankit... could you please tell the source of these questions?

LSAT Test

ankit1383,
could you please post the Official explanation.i cant follow the reasoning behind B

I'm pretty confident that C is correct answer.