Planetary bodies differ from one another in their composition, but mos

Question

Planetary bodies differ from one another in their composition, but most of those in the Solar System have solid surfaces. Unless the core of such a planetary body generates enough heat to cause volcanic action, the surface of the body will not be renewed for millions of years. Any planetary body with a solid surface whose surface is not renewed for millions of years becomes heavily pockmarked by meteorite craters, just like the Earth’s Moon. Some old planetary bodies in the Solar System, such as Europa, a very cold moon belonging to Jupiter, have solid icy surfaces with very few meteorite craters.

If the claims above are true, which one of the following must, on the basis of them, be true?

If the claims above are true, which one of the following must, on the basis of them, be true?

(A) The Earth’s Moon does not have an icy surface.

(B) If a planetary body does not have a heavily pockmarked surface, its core does not generate enough heat to cause volcanic action.

(C) Some planetary bodies whose cores generate enough heat to cause volcanic action do not have solid icy surfaces.

(D) Some of Jupiter’s moons are heavily pockmarked by meteorite craters.

(E) Some very cold planetary bodies have cores that generate enough heat to cause volcanic action.

GMATNinja · Accepted Answer

Start by understanding how the passage fits together:
 
Here, the author offers us a  contrast : some planetary bodies with solid surfaces become heavily pockmarked by meteorites, while some do not.

What is the difference between the pockmarked and un-pockmarked planetary bodies?

Well, according to the second sentence, the ONLY way that a solid surface can be renewed (and its pockmarks erased) is through volcanic action. If the surface is NOT renewed, there will be a large number of pockmarks. From this, we can start to see that any un-pockmarked solid-surfaced body MUST be volcanically active.

Then the author introduces Europa, which is a "very cold," solid-surface moon that has "very few meteorite craters" -- or, in other words, is largely un-pockmarked. From the above, we know that Europa MUST be volcanically active for this to be the case.

Based on the above, which answer choice MUST be true?
 
From the argument, we know that the Earth's Moon has a solid surface. But we have no idea what that surface is made of -- maybe it's ice, or maybe it's rock or some other solid material. The Earth's Moon  could  have an icy surface, so (A) doesn't HAVE to be true.

Eliminate (A).

The argument specifically discusses planetary bodies  with solid surfaces  -- THESE bodies can only be renewed through volcanic activity.

(B) talks about ALL planetary bodies, including those that DON'T have a solid surface. That would include bodies with liquid or gaseous surfaces. We have no idea how these other planetary bodies behave -- maybe they require volcanic activity to be renewed, and maybe not.

(B) doesn't have to be true, so get rid of (B).

The author tells us about one particular planetary body, which does have a solid icy surface.

Do we know it's true that other planetary bodies DON'T have a solid icy surface? Nope -- with only the info in the argument to work from, it's possible that ALL volcanically-active planetary bodies have icy surfaces.

(C) is out.

Again, we're only told about one specific body -- Europa. We really have no idea what is going on with the rest of Jupiter's moons. In fact, using only the info in the argument, we don't even know that Jupiter HAS additional moons! So we definitely can't infer what is going on with these other bodies.

Eliminate (D).

We know that Europa is "very cold." We also know that its solid surface is (largely) un-pockmarked, and that the ONLY way for that to be true is through volcanic activity. So, we know that this "very cold" body MUST be able to generate the heat required for volcanic activity.

(E) MUST be true, so (E) is the correct answer.

I hope that helps!

asaf · Answer

Between C and E.
C says if X leads to Y then Y should lead to X. Not alwyas true. So C is out.
E is what I pick.

boubi · Answer

i go for E
the stem clearly state on the basis of them"the claims"
looking at answer choices between E and C
only E can be based entirely on those claims.
Claims never talked about some volcanic bodies that do not have ice surface. But about a relation between volcanic activity and craters, here is hour link with answer E...since this icy planet has few craters then based on the claims it must have some volcanic activity thus...
Some Icy planet have volcanic activity
Hence E

gluon · Answer

My choice is E for the same reasons.

vineetgupta · Answer

Thanks...Great Explanation!!!...OA is E.

RanjanSury · Answer

A. No. Nothing of that sort is mentioned in the passage. The passage only states that Europa has an icy surface. Doesn’t mention anything about the surface of the moon as such. 
B. Very narrow. We can't say for sure. There could be a variety of other reasons. 
C.Again we aren't a 100% sure about this. 
D.This claims the opposite of what the passage says. 
E. Yes. Correct choice. Clue: Last line of the passage.

hellosanthosh2k2 · Answer

ContraPositive into play => E

if not enough heat to cause volcanic action(A) -> the surface of the body will not be renewed for millions of years(B) -> heavily pockmarked by meteorite craters (C)

contrapositive: ~C -> ~B -> ~A

Premise: Europa, a very cold moon belonging to Jupiter, have solid icy surfaces with very few meteorite craters (~C) - negation of heavily pockmarked by meteorite creaters

~C -> ~A => Europa (very cold) with very few metorite craters (~C) -> enough heat to cause valconic action (~A) (negation of not enough heat to cause valconic action)

Answer E captures the above contrapositive nicely, by saying some very cold planetary bodies (Europa) has enough heat to cause valconic action

radhikagagneja · Answer

kindly explain the reason for any option to be wrong or right

Crytiocanalyst · Answer

(A) The Earth’s Moon does not have an icy surface.
meteoritic activity doesn't rule out a possibility of a icy surface therefore out

(B) If a planetary body does not have a heavily pockmarked surface, its core does not generate enough heat to cause volcanic action.
It generates heat waves to create volcanic eruptions straight opposite therefore out

(C) Some planetary bodies whose cores generate enough heat to cause volcanic action do not have solid icy surfaces.
A far fetched assumption it may or may not happen

(D) Some of Jupiter’s moons are heavily pockmarked by meteorite craters.
We have absolutely no clue whether Jupiter has any more stars therefore out

(E) Some very cold planetary bodies have cores that generate enough heat to cause volcanic action.
This is a possibility which might happen therefore our answer

THerefore IMO E

behlmanmeet · Answer

Planetary bodies differ from one another in their composition, but most of those in the Solar System have solid surfaces. Unless the core of such a planetary body generates enough heat to cause volcanic action, the surface of the body will not be renewed for millions of years. Any planetary body with a solid surface whose surface is not renewed for millions of years becomes heavily pockmarked by meteorite craters, just like the Earth’s Moon. Some old planetary bodies in the Solar System, such as Europa, a very cold moon belonging to Jupiter, have solid icy surfaces with very few meteorite craters.

If the claims above are true, which one of the following must, on the basis of them, be true?

If the claims above are true, which one of the following must, on the basis of them, be true?

Solution:

(A) The Earth’s Moon does not have an icy surface.:  Irrelevant. Cannot be determined.

(B) If a planetary body does not have a heavily pockmarked surface, its core does not generate enough heat to cause volcanic action.:  Opposite to what has been said. If the core does not generate enough heat to cause volcanic action, the surface of the body will not be renewed and if the body doesn't get renewed then it gets heavily pockmarked with craters.

(C) Some planetary bodies whose cores generate enough heat to cause volcanic action do not have solid icy surfaces.:  Maybe true maybe not. We are not provided with relevant info on this.

(D) Some of Jupiter’s moons are heavily pockmarked by meteorite craters.:  No info about this.

(E) Some very cold planetary bodies have cores that generate enough heat to cause volcanic action.  By process of elimination, this must be the correct option. But we can also understand this because we are given that Europa has solid icy surfaces with very few meteorite craters. Thus, it must be able to renew its surface body, leading to fewer pockmarked meteorite craters.

unraveled · Answer

Planetary bodies differ from one another in their composition, but most of those in the Solar System have solid surfaces. Unless the core of such a planetary body generates enough heat to cause volcanic action, the surface of the body will not be renewed for millions of years. Any planetary body with a solid surface whose surface is not renewed for millions of years becomes heavily pockmarked by meteorite craters, just like the Earth’s Moon. Some old planetary bodies in the Solar System, such as Europa, a very cold moon belonging to Jupiter, have solid icy surfaces with very few meteorite craters.

If the claims above are true, which one of the following must, on the basis of them, be true?

If the claims above are true, which one of the following must, on the basis of them, be true?

Volcanic action ----> No pockmarked surface OR
No volcanic action ----> pockmarked surface created by meteorites(Earth's Moon's surface) ----> i.e. Earth's moon has no volcanic activity(inference)
 Jupiter's moon Europa ----> solid icy surfaces with very few meteorite craters ----> i.e. Some volcanic activity must have been there on Europa(inference) 
(A) The Earth’s Moon does not have an icy surface. - WRONG. Not inferable.

(B) If a planetary body does not have a heavily pockmarked surface, its core does not generate enough heat to cause volcanic action. WRONG. Goes against the argument altogether.

(C) Some planetary bodies whose cores generate enough heat to cause volcanic action  do not have solid icy surfaces . - WRONG. The problem with this option is that of the red text. We don't have causality given in the argument as far as solid icy surfaces are concerned. It does look to be true but icy thing loses out as it may or may not be true.

(D) Some of Jupiter’s moons are heavily pockmarked by meteorite craters. - WRONG. Irrelevant. May or may not be true.

(E) Some very cold planetary bodies have cores that generate enough heat to cause volcanic action. - CORRECT. If the last sentence is further continued, the flow of the argument would lead us to E. Europa is cold but has enough volcanic activity to lead to its surface with few meteorite craters.

Answer E.

kittle · Answer

Sajjad1994  - see here also

Some "old" planetary bodies in the Solar System, such as Europa, a very cold moon belonging to Jupiter, have solid icy surfaces with very few meteorite craters

It should not be "old" but "cold" - this interferes in reader's ability to get to the correct answer. I do not know who to raise this too but our platform should work towards ensuring "error-proof" questions. Thanks for cooperation.

Sajjad1994 · Answer

Well this is actually old and not cold, I just double checked it.

Danish234 · Answer

Hey  GMATNinja , As always great explanation and a top quality method to solve them explained beautifully. I solved them exactly the way which you explained.
But however I took 5 mins 44 secs to solve this question. I understand that this is a high level question but If there are any tips and tricks that might help us solve questions like this in a short amount of time can you share them? That would be greatly appreciated.
Thank You.

colorfuldreams · Answer

Any planetary body with a solid surface whose surface is not renewed for millions of years becomes heavily pockmarked by meteorite craters...... a very cold moon belonging to Jupiter, have solid icy surfaces with very few meteorite craters.

hence E

hence E

GMATNinja · Answer

I'm glad you found the explanation helpful!

Unfortunately, there really aren't any tricks or shortcuts that will allow you to answer tough questions quickly and accurately. Instead, it's best to develop a rock-solid process and then get lots of high-quality reps on official questions to hone and refine that technique. Eventually, your timing will improve as you become more comfortable with your process.

Some questions that you might ask yourself: during those 5 minutes 44 seconds, did you find yourself having to reread the passage multiple times? If so, how can you fix your first read-through of the passage to get what you need more efficiently? Same thing with the answer choices -- did you find yourself cycling through them quickly multiple times, or did you allow yourself time to think through each option in one pass? (Just to clarify: a bit of re-reading is okay and kind of inevitable, but if it is excessive then you'll want to change your process).

A final thought is that you definitely don't want to spend that long on a CR question in the test. So, if you notice yourself spinning your wheels, it might be best to move on to the next question. You'll want to be prepared to pull the plug on a particularly difficult problem to ensure that you have time for the rest of the section.

No silver bullets here, sadly, but I hope that helps a bit!

VerbalBot · Answer

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