Nature constantly adjusts the atmospheric carbon level. An increase in

Question

Nature constantly adjusts the atmospheric carbon level. An increase in the level causes the atmosphere to hold more heat, which causes more water to evaporate from the oceans, which causes increased rain. Rain washes some carbon from the air into the oceans, where it eventually becomes part of the seabed. A decrease in atmospheric carbon causes the atmosphere to hold less heat, which causes decreased evaporation from the oceans, which causes less rain, and thus less carbon is washed into the oceans. Yet some environmentalists worry that burning fossil fuels may raise atmospheric carbon to a dangerous level. It is true that a sustained increase would threaten human life. But the environmentalists should relax—nature will continually adjust the carbon level.

Which one of the following, if true, would most weaken the argument in the passage?

(A) Plant life cannot survive without atmospheric carbon.
(B) It is not clear that breathing excess carbon in the atmosphere will have a negative effect on human life.
(C) Carbon is part of the chemical “blanket” that keeps the Earth warm enough to sustain human life.
(D) Breathing by animals releases almost 30 times as much carbon as does the burning of fossil fuels.
(E) The natural adjustment process, which occurs over millions of years, allows wide fluctuations in the carbon level in the short term.

Source: LSAT

shashankism · Accepted Answer

Short Story : 1. Nature constantly adjusts the atmospheric carbon level.
2. /\ in the level causes the atmosphere to hold more heat, which causes more water to evaporate from the oceans, which causes /\ rain.
3. Rain washes some carbon from the air into the oceans, where it eventually becomes part of the seabed.
4. \/ in atmospheric carbon causes the atmosphere to hold less heat, which causes decreased evaporation from the oceans, which causes less rain, and thus less carbon is washed into the oceans. 
5. some environmentalists worry that burning fossil fuels may raise atmospheric carbon to a dangerous level.
 6. sustained increase would threaten human life.

Conclusion : Environmentalists should relax—nature will continually adjust the carbon level.

The question asks to find the statement which  most weakens the conclusion.

(A) Plant life cannot survive without atmospheric carbon. 
Out of scope. As the passage says that the level of carbon will be maintained by nature.

(B) It is not clear that breathing excess carbon in the atmosphere will have a negative effect on human life. 
Breathing excess carbon in atmosphere will have -ve effect on human life. So, it surely is a problem. But if nature will maintain the level of carbon in atmosphere, there won't be any problem. This doesn't weaken the conclusion.

(C) Carbon is part of the chemical “blanket” that keeps the Earth warm enough to sustain human life. 
This is again a fact but it doesn't weaken the conclusion.

(D) Breathing by animals releases almost 30 times as much carbon as does the burning of fossil fuels. 
Breathing by animals releases almost 30 times as much carbon as by burning the fossil fuel. But it is happening from ages. Only extra burden is created by the burning of fossil fuel and hence it has created problem. So this statement is out of scope.

(E) The natural adjustment process, which occurs over millions of years, allows wide fluctuations in the carbon level in the short term. 
Now this point really weakens the conclusion. Since nature adjustment process will take million years and hence short term fluctuation in carbon level is allowed by nature. So, during that time, the increased level of carbon in nature will threaten human life & hence environmentalists should not relax.

So, my answer is E. Waiting for OA to be posted.

Bunuel · Answer

Official Explanation

The counter-premise in this argument is the sentence “It is true that a sustained increase   would threaten human life.” By making this concession, the author shows that he is aware of the alternatives and the potential seriousness of situation; it also provides a hedge against potential criticism that the situation is too important to risk following his advice.

The question asks us to weaken the argument. As mentioned before, to weaken an argument typically you attack a premise (either expressed or suppressed) of the argument. Now someone who did not fully understand the author’s main point might mistake the counter-premise for a premise. Look at answer choice (B); it directly attacks the counter-premise by implying that it may not be true. The LSAT writers offer (B) as bait. They know that some people will fall for it because it attacks a statement in the argument, as should the answer. The best answer, however, will attack the main premise.

One possibility the author did not account for is that the natural adjustment process may require many years and that in the short run dangerous levels of carbon could accumulate. This directly attacks the main premise of the argument, “Nature  constantly  adjusts the atmospheric carbon level.”  Hence the answer is (E).

It is often clarifying to outline an argument’s logical structure. An outline can make clear the argumentative strategy the author is using. The above argument has the following structure:

Main Premise 
  Explanation of Main Premise 
  Secondary Premise 
  Counter-Premise 
  Conclusion

The first sentence introduces the main premise that nature constantly adjusts the atmospheric carbon level. The next three sentences explain that premise. Then in the fifth sentence, the secondary premise is introduced that environmentalists are concerned that burning fossil fuels may increase atmospheric carbon to dangerous levels. Then the penultimate (next to last) sentence introduces the counter-premise that an increase in the carbon level would be a threat to human life. This measures the conclusion that environmentalists should relax because nature will adjust the carbon level.

Skywalker18 · Answer

E.The author concludes that environmentalists are wrong to worry about increased carbon levels due to the burning of fossil fuels, because nature will continually adjust the carbon level. However, if, as choice (E) states, the adjustment process works very slowly, allowing wide short-term fluctuations in the carbon level, then it’s conceivable that dangerous or even lethal levels of carbon can build up, thus severely weakening the author’s argument: the environmentalists would be right to worry.

(A), (C) The author doesn’t debate the necessity of carbon, she merely argues that nature takes care of the carbon level by itself, and that the environmentalists should chill.
(B) Some may feel that this weakens the author’s concession in the last sentence, but even if it did, that sentence is basically a tangential point that has little todo with the logic of the argument, which deals with nature’s regulation of the carbon level. However, this probably doesn’t even affect the author’s concession, because that statement never said or implied that the threat to humans of increased carbon levels would come from breathing it in; it would likely be more indirect, along the lines of the processes described.
(D) This is an irrelevant comparison that has no bearing on the logic of the argument.

unraveled · Answer

Nature constantly adjusts the atmospheric carbon level. An increase in the level causes the atmosphere to hold more heat, which causes more water to evaporate from the oceans, which causes increased rain. Rain washes some carbon from the air into the oceans, where it eventually becomes part of the seabed. A decrease in atmospheric carbon causes the atmosphere to hold less heat, which causes decreased evaporation from the oceans, which causes less rain, and thus less carbon is washed into the oceans. Yet some environmentalists worry that burning fossil fuels may raise atmospheric carbon to a dangerous level. It is true that a sustained increase would threaten human life. But the environmentalists should relax—nature will continually adjust the carbon level.

Which one of the following, if true, would most weaken the argument in the passage?

(A) Plant life cannot survive without atmospheric carbon. - WRONG. Plain generic statement that passage is not about.
(B) It is not clear that breathing excess carbon in the atmosphere will have a negative effect on human life. - WRONG. Scope shift. Not impacting passage.
(C) Carbon is part of the chemical “blanket” that keeps the Earth warm enough to sustain human life. - WRONG. That we already know from the passage.
(D) Breathing by animals releases almost 30 times as much carbon as does the burning of fossil fuels. - WRONG. So, its a natures part only thus a strengthener.
(E) The natural adjustment process, which occurs over millions of years, allows wide fluctuations in the carbon level in the short term. - CORRECT. If adjustment occurs for a longer period of time as compared to fluctuation that may lead to extreme situation then there is trouble.

Answer E.

VerbalBot · Answer

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