The most reliable method to detect the presence of life on a planet wo

Question

The most reliable method to detect the presence of life on a planet would be by determining whether or not its atmosphere contains methane. This is because methane completely disappears from a planet's atmosphere through various chemical reactions unless it is constantly replenished by the biological processes of living beings.

Which one of the following statements, if true, most seriously weakens the argument?

A. There are other ways of detecting the presence of life on a planet.

B. Not all living beings have the ability to biologically produce methane

C. We are incapable at present of analyzing a planet's atmosphere for the presence of methane.

D. Some living beings biologically produce only very small amounts of methane

E. Earth is the only known planet whose atmosphere is known to contain methane

inimeg · Answer

Conclusion: living beings produce methane gas, so finding methane in atmosphere is proof that life exists

Argument B states that not all living being produced methane, thus it is directly targeting the conclusion and weakening it as there may be life forms which do not produce methane biologically and would be present.

Posted from my mobile device

nikitathegreat · Answer

Can someone explain why option D is incorrect? If they produce very small amounts of methane then the atmosphere will not have much effect

ABHRAJIT · Answer

D says that ‘some’ produce very small amounts of methane, now we don’t know how much this ‘some’ means. It can be 1% or it can be 20%. Also even if some living beings produce very small amounts of methane, it doesn’t weaken the conclusion that methane is getting replenished.

B says that Not all living beings are capable of producing methane which suggests that there might be living beings present despite absence of methane in the atmosphere. This weakens the conclusion.

Hope it helps.

Posted from my mobile device

ttiger21 · Answer

Why is C wrong? Can you walk through how you eliminated the other answer choices? Thank you!

ABHRAJIT · Answer

Even if C is true, it doesn’t weaken the argument that determining presence of methane would be the most reliable method. Just because at present we are incapable doesn’t help conclude about the reliability of a method.

A is wrong because even if there are other ways , it doesn’t imply that determining methane presence is not the most reliable method. There can be other methods and methane method can still be the best.

E is wrong for the same reasons. Even if E is true, conclusion isn’t weakened. You can still say methane method is most reliant and find no methane in the planet’s atmosphere, and the conclusion will still hold.

Reasons for D is mentioned in my above post.

Hope this helps.

Posted from my mobile device

egmat · Answer

The Core Argument: 
Methane detection is reliable because methane only stays in an atmosphere if living beings constantly replenish it.  Therefore , methane = life.

Why C is Wrong: 
C says: "We  cannot currently  analyze atmospheres for methane."

Here's the  trap : C attacks our  ability to use  the method,  not  the method's  reliability .

Think of it this way:
- A locked car is still a reliable car - you just can't access it  yet 
- Similarly, even if we can't detect methane  today , the method could still be perfectly reliable  once we develop the technology

C is a  practical limitation , not a logical flaw.

Why B is Correct: 
B says: "Not all living beings produce methane."

This  directly attacks the logic :
- If some life forms  don't  produce methane → a planet could have life but  NO  methane
- We check → find no methane → conclude "no life" →  WRONG 
- The method gives  false negatives  =  unreliable

Quick Elimination: 
-  (A)  "Other methods exist" — Doesn't weaken methane's reliability
-  (D)  "Small amounts" — Still produces methane, still detectable
-  (E)  "Earth is the only known planet" — Irrelevant to reliability

For  Weaken questions , always attack the  LOGIC  of the argument, not the  logistics  of implementing it.

Answer: B

The most reliable method to detect the presence of life on a planet wo

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Critical Reasoning (CR) Questions

The most reliable method to detect the presence of life on a planet wo

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards