Q22 - When a planetary system forms,

[pgerretsen]

I do not understand how D is right. I put C. Could somebody please explain? Thanks.

[peg_city]

Yes, someone please explain

Especially when the passage says

"Without Jupiter and Saturn, whose gravitational forces have prevented earth from being Frequently struck by large comets"

It basically says (D) it in the passage; "Fredquently"

[ManhattanPrepLSAT1]

"Without Jupiter and Saturn, whose gravitational forces have prevented earth from being Frequently struck by large comets"

It basically says (D) it in the passage; "Fredquently"

Great eye! I think you knew what to do on this one, but got tripped up at the end.

The conclusion is about the chance that intelligent life will emerge. That conclusion depends on a series of probabilities; the chance that a planet capable of supporting life will be formed, the chance that a large planet the size of Jupiter or Saturn will be formed, and the chance that large comets would strike the planet.

Notice that the first two claims are about nowhere in particular. The third claim, as it appears in the argument, is about Earth. The conclusion of the argument, however, is about nowhere in particular. So while we know that comets would have hit the Earth "frequently," that's not a broad enough claim to establish a conclusion about other planetary systems.

Answer choice (D) pushes that frequency out and would help us evaluate the conclusion. If those other planetary systems are likely to have comets then the argument would be supported. However, if the planetary system was unlikely to have comets, the conclusion would be challenged.

Does that answer your question?

[lhermary]

Why is B wrong?

[ManhattanPrepLSAT1]

The conclusion is about the likelihood of life emerging on a planet, but answer choice (B) is about intelligent life surviving a comet strike. So it addresses whether the life would continue to exist, but it couldn't help to figure out what the chances of life emerging on a planet.

Does that answer your question?

[iridium77]

Why is B wrong?

Also, the stimulus only describes that it is impossible that intelligent life would have survived frequent collisions by asteroids whereas b.) describes likelihood of intelligent life surviving a single collision.

[aznriceboi17]

For any particular planet, do we not have to be concerned with comets coming from outside its planetary system? I eliminated (D) because it didn't rule out the threat of comets originating outside the planetary system hitting the planet (perhaps most comet strikes involve a planet and a comet outside its planetary system), and ended up choosing (B).

[christine.defenbaugh]

For any particular planet, do we not have to be concerned with comets coming from outside its planetary system? I eliminated (D) because it didn't rule out the threat of comets originating outside the planetary system hitting the planet (perhaps most comet strikes involve a planet and a comet outside its planetary system), and ended up choosing (B).

Great question aznriceboi17!

Let's take a look at exactly what the question is asking. We want to know which thing would be most useful to know in order to evaluate the argument. In other words, which thing could either strengthen or weaken the argument. The question is not asking which of the answer choices would or could guarantee the conclusion.

As a result, (E) doesn't have to fully guarantee the conclusion either way - it just has to have the capability of making the conclusion more or less likely.

I agree with you that knowing how likely it is that comets can come from outside the planetary system is also useful information to have. But the fact that that would be useful information also doesn't make the information in (E) suddenly not useful!

Imagine if you wanted to know whether a typical dinner at one restaurant was more expensive than a typical dinner at another. It would be useful to know whether the appetizers at Restaurant A were more expensive on average than the appetizers at Restaurant B. Even if they are, though, that doesn't rule out that perhaps the entrees at Restaurant B are WAY more expensive than at Restaurant A!

Both pieces of information are useful, and neither one would guarantee the conclusion on its own.

The critical element is understand your task on this question. It's asking us what is useful, not what would guarantee the conclusion.

Does that help a bit?

[coco.wu1993]

I can't believe the correct answer hinges on a single word in the stimulus I didn't see that word and missed this one.

[logicfiend]

I originally choose (B) as well here, and upon reviewing changed it to (D).

You actually need to be asking yourself the question in (D) to see the relevance of (B).

Is it relevant to the argument whether intelligent life could survive if a comet hit, without first assessing whether a comet would hit AT ALL?

If "frequency" means one comet comes around the system every 10 million gazillion years, then the conclusion would appear to be challenged—maybe we really don't need large planets then.

Asking if intelligent life could survive is the second question you would ask after first establishing whether frequency really poses an issue at all.

That's how I came to D, if that helps anyone.