Every element on the periodic chart is radioactive, although the most

Question

Every element on the periodic chart is radioactive, although the most stable elements have half-lives which are thousands and thousands of years long. When an atom decays, it splits into two or more smaller atoms. Even considering the fusion taking place inside of stars, there is only a negligible tendency for smaller atoms to transmute into larger ones. Thus, the ratio of ligther to heavier atoms in the universe is increasing at a measurable rate.

Which of the following sentences provides the most logical continuation of this paragraph?

(A) Without radioactive decay of atoms, there could be no solar combustion and no life as we know it
(B) Therefore, it is imperative that scientists begin developing ways to reverse the trend and restore the proper balance between the lighter and heavier elements
(C) Consequently, it is possible to use a shifting ratio of light to heavy atoms to calculate the age of the universe
(D) Therefore, there are now more light elements in the universe than heavy ones
(E) As a result, the fusion taking place inside stars has to produce enough atoms of the heavy elements to offset the radioactive decay of large atoms elsewhere in the universe.

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rishabh1105 · Answer

Every element on the periodic chart is radioactive, although the most stable elements have half-lives which are thousands and thousands of years long. When an atom decays, it splits into two or more smaller atoms. Even considering the fusion taking place inside of stars, there is only a negligible tendency for smaller atoms to transmute into larger ones. Thus, the ratio of ligther to heavier atoms in the universe is increasing at a measurable rate.

Which of the following sentences provides the most logical continuation of this paragraph?

(A) Without radioactive decay of atoms, there could be no solar combustion and no life as we know it
Long shot conclusion

(B) Therefore, it is imperative that scientists begin developing ways to reverse the trend and restore the proper balance between the lighter and heavier elements
Nothing has been told if this is a concerning effect. So doesnt make sense

(C)  Consequently, it is possible to use a shifting ratio of light to heavy atoms to calculate the age of the universe
Makes sense. We can use the information of half life of elements and their quantities to calculate age of the universe.

(D) Therefore, there are now more light elements in the universe than heavy ones
Long shot. We dont know

(E) As a result, the fusion taking place inside stars has to produce enough atoms of the heavy elements to offset the radioactive decay of large atoms elsewhere in the universe.
Long shot. We dont know

Dereno · Answer

The passage speaks about the concept of radioactive decay. Every element has its own pace of decay. Sometimes, the decay can be for a greater period of time - say for more than thousand of years. The author is trying to bring the time frame into account.

And, the atoms split from heavier atoms to lighter and simpler atoms. This has eventually led to suspension of more lighter atoms when compared to the heavier atoms. Even though, the fusion of stars which takes in all smaller atoms fusing together to become a larger atom. This process is negligible. Hence, the ratio of smaller atoms to larger atoms is increasing at a greater measurable rate.

Let’s look into options.

(A) Without radioactive decay of atoms, there could be no solar combustion and no life as we know it.

This is a true statement, but it doesn't really follow logically the paragraph. It introduces a new topic (solar combustion and life). Hence out of scope. 
 
  (B) Therefore, it is imperative that scientists begin developing ways to reverse the trend and restore the proper balance between the lighter and heavier elements.

The author has not mentioned anything as warning or upcoming danger if this trend keeps persisting. Hence out of scope. 
 
  (C) Consequently, it is possible to use a shifting ratio of light to heavy atoms to calculate the age of the universe.

This option directly follows the paragraph's logic. If the ratio is changing at a measurable rate, scientists could use that rate to estimate how long the change has been happening. Decay rate can provide a timeline. 
 
  (D) Therefore, there are now more light elements in the universe than heavy ones.

This is mentioned in the passage, but cannot be taken as a concluding statement. 
 
  (E) As a result, the fusion taking place inside stars has to produce enough atoms of the heavy elements to offset the radioactive decay of large atoms elsewhere in the universe.

No mention of events occurring elsewhere in the universe is quoted by the author. Hence, out of scope.

Option C

mithileshk · Answer

Option C

Very logical ! 
 Paragraph describes a  systematic, measurable trend  → lighter atoms increasing. 
 Using that trend to  calculate the age of the universe  makes perfect sense! 
  Natural scientific extension : "Since the ratio is shifting, we can use it as a clock."

Why to reject D(other close option)?

Paragraph only says the  ratio is increasing . 
 It  does not claim  there are  already more  light atoms than heavy. 
 The shift is happening, but maybe still heavy atoms are more (just at a decreasing rate).

Bunuel · Answer

Official Explanation

The last sentence of the paragraph is very important. It tells us that the proportion of light atoms in the universe is increasing (because heavy ones decay into light ones, but the reverse process does not occur) and that this trend can be measured. By extrapolation back into time on the basis of present trends, scientists can find out when it all began.

(B) and (E)  are incorrect for the same reason. The author describes a physical phenomenon occurring on a grand scale. There is no hint that it will be possible for scientists to reverse it  (B) .

Further,  (E)  is in direct contradiction with information given in the paragraph: The ratio is not stable because the stars do not produce enough heavy atoms to offset the decay.

(D)  cannot be inferred from the passage. Although the ratio of light to heavy atoms is increasing, we should not conclude that the ratio is greater than 1:1. And, in any event, this would not be nearly so logical a conclusion to the passage as  (C) .

Finally,  (A)  is a distraction. It picks up on a minor detail in the passage and inflates that into a conclusion. Moreover, the passage clearly states that the process which keeps the stars going is fusion, not decay.

The correct answer is (C).

Anandanwar · Answer

Hello,
A query here.
The passage does not state the measurable rate has been same from the beginning of time. Also it does not state that the rate of change which existed in the past is known.

So we cannot really fo with C.

Could someone please point out the problem in this logic?
Regards,
Ankit

guddo · Answer

Every element on the periodic chart is radioactive, although the most stable elements have half-lives which are thousands and thousands of years long. When an atom decays, it splits into two or more smaller atoms. Even considering the fusion taking place inside of stars, there is only a negligible tendency for smaller atoms to transmute into larger ones. Thus, the ratio of lighter to heavier atoms in the universe is increasing at a measurable rate. 
 
Which of the following sentences provides the most logical continuation of this paragraph?

The paragraph explains that heavy atoms gradually become lighter atoms through radioactive decay, while the reverse process is negligible.  The key idea  is that the ratio of light atoms to heavy atoms changes over time at a measurable rate. So the best continuation should use that changing ratio as a  time-measuring tool .

(A) Without radioactive decay of atoms, there could be no solar combustion and no life as we know it.

This is not supported. The paragraph discusses radioactive decay and atomic ratios, not whether life or solar combustion depends on radioactive decay.

(B) Therefore, it is imperative that scientists begin developing ways to reverse the trend and restore the proper balance between the lighter and heavier elements.

This is not logical. The paragraph describes a natural trend, but it does not suggest that the trend is harmful or needs to be reversed.

(C) Consequently, it is possible to use a shifting ratio of light to heavy atoms to calculate the age of the universe.

This is correct. If the ratio of lighter to heavier atoms is increasing at a measurable rate, then that ratio can potentially be used to estimate how much time has passed.

(D) Therefore, there are now more light elements in the universe than heavy ones.

This does not follow. The ratio is increasing, but that does not prove that light elements currently outnumber heavy elements.

(E) As a result, the fusion taking place inside stars has to produce enough atoms of the heavy elements to offset the radioactive decay of large atoms elsewhere in the universe.

This is the opposite of the paragraph. The paragraph says the tendency for smaller atoms to become larger ones is negligible, so fusion does not offset the general shift toward lighter atoms.

Answer: (C)

egmat · Answer

Hi Anandanwar,

Your instinct about what a  reliable  age calculation would need is actually good science: yes, to nail down a real number you'd want to know how the rate behaved in the past. But notice what standard this question is holding the answer to, and notice the exact words in (C).

This is a "most logical continuation" question, not a strict inference question.  You're evaluating (C) as if it has to be fully  provable  from the passage. That's the standard for an inference/must-be-true question. Here the job is only to pick the sentence that flows most naturally from the last line -  "the ratio... is increasing at a measurable rate."

Now read (C)'s own wording:  "it is possible to use a shifting ratio... to calculate the age of the universe."  The claim is hedged -  "it is possible to use"  - not "scientists can precisely compute." A soft "it is possible" claim does  not  require you to already know the exact historical rate. The passage gives you a  measurable  rate of change, and a measurable rate of change is exactly the kind of thing that can serve as a clock. That's all (C) leans on.

So the constant/known-rate requirement you're importing belongs to a much stronger statement than the one (C) actually makes.

Watch the word turn

-  "it is possible to use..."  (the real choice) - only needs a measurable trend. Supported.
- If (C) instead said  "scientists can now precisely calculate the exact age"  -  now  your objection lands, because that would demand the historical rate be known.

See how your critique only bites the stronger version? Turning that one knob is the whole difference.

And remember the bar is  relative  - you pick the  best  continuation. (A) is off-scope, (B) invents a danger, (E) contradicts the "negligible fusion" premise, and (D) overreaches on quantity. Against that field, the modest, on-topic (C) is clearly the most logical follow-on.

Answer: C

Every element on the periodic chart is radioactive, although the most

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Every element on the periodic chart is radioactive, although the most

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