radhikagagneja wrote:
kindly explain the reason for any option to be wrong or right
Start by understanding how the passage fits together:
Quote:
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.
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?
Quote:
(A) The Earth’s Moon does not have an icy surface.
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).
Quote:
(B) If a planetary body does not have a heavily pockmarked surface, its core does not generate enough heat to cause volcanic action.
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).
Quote:
(C) Some planetary bodies whose cores generate enough heat to cause volcanic action do not have solid icy surfaces.
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.
Quote:
(D) Some of Jupiter’s moons are heavily pockmarked by meteorite craters.
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).
Quote:
(E) Some very cold planetary bodies have cores that generate enough heat to cause volcanic action.
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!
, 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.