Q11 - A bacterial species will inevitably

[ilona11223344]

I have a question as to why (B) is better than (E)? Is it because you can't assume that any antibiotics have been used against species X for a few years? Thanks!

[LSAT-Chang]

I have a question as to why (B) is better than (E)? Is it because you can't assume that any antibiotics have been used against species X for a few years? Thanks!

(E) is just not something that is supported in the argument above. (E) is making a comparison between the resistance of bacterial species X to antibiotics prior to being used against it and after being used against it. But there is absolutely no comparison being made between the two from the stimulus.

I think this question works nicely if we just add a little time to diagramming it (took me about a minute or less to solve this one with the diagram):

NOT develop greater resistance to antibiotic --> eliminated species completely

CANNOT eliminate species completely --> ???

We are told in the second sentence that there is no single antibiotic now on the market powerful enough to eliminate bacterial species X completely. So what do we know??

The contrapositive of the first sentence tells us that the bacterial species WILL develop greater resistance to antibiotic being used against it, which is nicely phrased in (B).

[ManhattanPrepLSAT1]

Nice work So!

You have the logic here nailed. This is definitely a contrapositive of the first statement. If you don't mind I'll show you how'd I'd set it up...

~DGR ---> E
CAntiB ---> ~E

From these we can conclude that if a current antibiotic is exposed to the bacterial species X, the bacteria will develop greater resistance.

CantiB ---> DGR

I might not have reached for the conditional logic here, but I'm glad it was a tool you felt comfortable using to identify the correct answer choice. I rely on it heavily and this is definitely an appropriate place to pull out that tool.

Lets look at the correct answer choices:

(A) is a baseless prediction, since the claims are only about what is presently the case.
(C) is untrue. It may be true that the only present way for antibiotics to completely destroy bacterial species X is through a combination of two or more of them, but there could be other ways of eliminating bacterial species X that do not involve antibiotics.
(D) plays on an interesting term. Virulence is the degree of pathogenicity - not important exactly what it means but it does not mean "resistance" to antibiotics. We might never make progress on beating bacterial species X, but if we never use antibiotics on them, they may never develop greater resistance to them nor become more virulent.
(E) is untrue. We don't know whether any antibiotics have been used agains bacterial species X.

Let me know if you have further questions on this one!

[aznriceboi17]

Is the fact that we don't know if any antibiotics have been used against X the only reason why people eliminated E? Even if you suppose that NO antibiotics have ever been used against X, then isn't E a vacuous truth?

My understanding was that if any antibiotic had been used against X, then because of the premise in the first sentence, would've developed greater resistance. It seemed that if anything E was a weaker form of the conclusion you could make, which is that X is more resistant to all antibiotics that have been used against it.

EDIT: I guess another criticism of E is that even if you grant that some antibiotics have been used against X, it's possible that they were also used for the first time against X only very recently -- in particular, to recent for the necessary 'few years' to have passed for X to develop greater resistance.

[ohthatpatrick]

Let’s explore the "˜vacuous truth’ angle ... I’ve never heard that term before but I surmise I get what it means.

So let’s say no antibiotics have ever been used against X.

Is it true to say "X is more resistant to some antibiotics that have been used against it than it was before they were used"?

No, it really can’t be true. The statement is not conditional. It makes a positive claim that this species *is* more resistant to antibiotics that *have* been used against it.

So if no antibiotics have ever been used against X, then (E) is full-fledged false.

I think your EDIT comment is a good angle ... we could have used some antibiotics on X yesterday, and we would not necessarily yet see X be more resistant to it.

You should also consider that the first sentence says
IF an antibiotic doesn’t eliminate completely "”> bacteria develops more resistance

We know that all antibiotics on the market TODAY can’t eliminate X completely, but (E) does not specify whether the antibiotics in question are ones on the market today. So (E) could also be falsified by considering antibiotics NOT on the market that DO eliminate X completely, in which case the conditional would not apply to those antibiotics.

Hope this helps.

[aznriceboi17]

Thanks Patrick. The 'some antibiotics used in the past may have been able to completely eliminate X' was very helpful -- I wish I had thought of that!

[jwms]

I initially circled (B) on the test, then took (E).

My rationale for going against (B) was that it says: 'if any antibiotic now on the market is used ...' to me, this left the door open to it being used in conjunction with another antibiotic, thus making it outside of the scope of the stimulus' 'no single antibiotic now on the market...'.

How should I correct this thinking? I occasionally have incorrect ACs using this line of thinking.

[dhlim3]

I still don't understand the explanation on why E is wrong, but I eliminated it based on the fact that it never mentions anything about the antibiotics being on the market. Perhaps there may be at least one prototypical antibiotic in existence that is not out on the market yet that is not ever possible for the bacterial species X to develop resistance to. I know this is a weak reason though.

All came down to details on this one.

[redskateboard]

I initially circled (B) on the test, then took (E).

My rationale for going against (B) was that it says: 'if any antibiotic now on the market is used ...' to me, this left the door open to it being used in conjunction with another antibiotic, thus making it outside of the scope of the stimulus' 'no single antibiotic now on the market...'.

How should I correct this thinking? I occasionally have incorrect ACs using this line of thinking.

I'm with you on B. If it had said. "...any [single] antibiotic..." then I would have picked it. I eliminated it because it didn't mention single. Why is it right the answer?

[ohthatpatrick]

I'm not quite understanding how combining antibiotics has anything to do with what (B) is claiming.

Let's say that X-Away is an antibiotic now on the market.

What do we know about it based on the stimulus?

We know from the last sentence, that X-Away, by itself, is not powerful enough to eliminate X completely.

What does the first sentence tell us about antibiotics that aren't powerful enough to eliminate a bacterial species?

The 1st sentence says, "if an antibiotic can't eliminate a species completely, then the species will inevitably develop greater resistance within a few years to it."

So we know that if X-Away is used to treat bacterial species X, then X will inevitably develop greater resistance within a few years to X-Away.

That's what (B) is saying would apply to ANY antibiotic we pick, provided it's available on the market.

Do you disagree with any of the inferences we made there? If not, then (B) is correct. Anything available on the market does not have the power by itself to kill X, thus, according to the 1st sentence, X will develop greater resistance to it in the future if we use it against X.

===

In terms of lingering (E) confusion, I think we found 3 reasons (so far), each of which is sufficient to strike it down.
1. There's no evidence that any antibiotic has EVER been used against X
2. Bacteria develops greater resistance "within a few years", so it's possible that we only recently started using antibiotics on X and X hasn't had time to develop any increased resistance.
3. This answer choice could be invalidated by antibiotics that are NOT now on the market.

[redskateboard]

Does the "any" in answer choice B mean any ONE anti-biotic used by itself? I don't think it means that. I think it leaves open the possibility that two anti-biotics are used at the same time. This can lead to a scenario where the stimulus is true but the statement in B in false.

So X-Away alone leads to greater resistance and X-DieNow ALONE also leads to greater resistance, but perhaps when used together they are strong enough to completely eliminate the species of bacteria.

[yeaea]

Ok, I’ve been thinking about this for a long time, and I guess B seems like the best of bad answers for this question. However, It still seems like B can’t be correct.

Imagine this scenario: Antibiotic 1 and antibiotic 2, when used in combination, can eliminate X completely.

If antibiotic 1 is used ONLY when antibiotic 2 is also used, X will never have a chance to develop greater resistance to antibiotic 1.

I can’t think think of a reason why this scenario is impossible. If this scenario is possible, I do not understand how B can be correct.