Critical Reasoning

Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

Which of the following would it be most important to ascertain in evaluating the argument?

(A) Whether populations of the other species on which deer tick larvae feed are found only in the areas also inhabited by white-footed mice.
(B) Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on.
(C) Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice.
(D) Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed.
(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans.

Is it A. It might imply that the deer ticks have an inclination to the white footed mice.

Well, I think its B.

If the size is dependent on the variety of the animals on which the deer tick feeds, then large deer tick population will imply its being fed on other animals, which supports the conclusion.

What's the OA?

for me it was between b and d...since we are concerned with infected larve...i chose D...

IMO B.

OA plz...

Well, we learn that the deer ticks, as larvae, pick up the bacteria that causes Lyme disease by eating these infected white-footed mice.

But do they eat these mice because they prefer them (do they like the taste?) or because they don't have any other source of food available?

We don't know...but this is what we would really want to know in order to evaluate the claim that we could stop (or slow down) the deer ticks from picking up the bacteria by increasing the supply of infection-free food sources. If the reason they eat the mice is preference, then increasing the population of infection-free food, won't make a difference.

Choice B matches this insight.

Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these species increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

we have already been told that there are some other species on which larvae feed,..

secondly, we are not concerned with the population of deer ticks we are concerned with them picking the bacterium...

Yes, we are told that there are infection-free food sources. But we have not been told that the deer ticks prefer those food sources to the infected white-footed mice.

We need to evaluate the claim that increasing the supply of infection-free food sources will curb the rate at which the deer ticks pick up the bacteria that causes lyme disease.

If the population of deer ticks is currently limited by food availability, then increasing the supply of infection-free food sources should slow the rate at which they pick up the bacteria, as it would suggest that the reason they were eating the mice was lack of other alternatives.

However, if the population of deer ticks is NOT limited by food availability, then increasing the supply of infection-free food sources would likely not slow the rate at which they are picking up the bacteria becuase it would suggest the reason they were eating the mice was preference (not because they had to).

But do they eat these mice because they prefer them (do they like the taste?) or because they don't have any other source of food available?

Oh, sorry for the confusion 2010gmat. Small error here on my part. What I should have wrote was:

"But do they eat these mice because they prefer them (do they like the taste?) or becase the supply of alternative food sources is limited."

uptowngirl 92, please search before posting questions. We have two different threads on the same question at the same time.

makes sense...can we have the OA pls...

I got a PM stating to post the OA:
First of all yes there are two different questions:the other one is:
https://www.beatthegmat.com/deer-ticks-t13441.html

@Testluv:Since the questions are different I started a new thread

This is a gprep question and I was hoping one of you had encountered it or maybe one of the verbal experts can break it down and explain it to us.I tried searching in google but everywhere the oa is debatable.

Hi uptowngirl92,

thanks a lot. Haven't seen this question before, unfortunately...the OA (which, by the way, I think you forgot to post!) is in contention?

Well, choices A and D are the only other two choices I seriously considered. In an evaluate the argument question, oftentimes the best way to evaluate the potential relevance of an answer choice is to think about the answer choice at its extremes, and then to compare the extremes to the argument (which needs to be kept clear in your head).

Applying this to choice A: if the safe species are not found in areas where there are no mice, there is no problem because there are no mice, and if they are found in mice-having as well as non-mice-having areas, again, there is no problem. In both cases, there is no obvious reason for thinking that the plan's chances will be hurt.

choice D: if an uninfected adult deer tick can pick up the disease by eating the deer on which infected larval deert ticks fed on, then that problem exists whether or not we implement the plan argued for by the author.

I posted above as to why I think the OA should be B....I do hope that helps, I know this is a tough and confusing question!

IMO D

Thanks testluv..I guess i'll go with you..the explanation makes sense!!

Hip Hip Hurray ..I did answered this tough one correctly...

@uptowngal Thx for posting such a wonderful CR!!