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.

[Had a really hard time understand the approach of the question and how to eliminate choices. Could only eliminate one answer choice. Any help / insight on how one could reach the actual answer????]

Oops. Updated. Thanks for the catch.

B..i think

if the population of deer tick increases with addition of new species to feed, possibility of the disease increase further. The white mice population is not reduced anyway.

IMO D....OA plz

Agree with A but largely through POE. Author's main argument: "If the population of these species [i.e., other species on which the larvae feed that do not harbor the bacterium] increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline."

My personal logic for A may seem a bit of a stretch, but the first two sentences of the paragraph imply that the tick is the agent for transmitting the bacteria. If the non-infected species are living amongst the white-footed mice (and, as a result, the ticks that are feeding off of these infected mice), these other species are at risk of acquiring the bacterium and, as a result, at risk of becoming just like the bacterium-infected white-footed mice themselves.

Reasons why others seem to be good candidates for elimination:

B.) This one looks like a trap because of the way that "population" is used. The author is not concerned with the deer tick population size but rather the population size of non-infected other species.

C.) Same as B - argument says if population of non-infected species increased -> number of ticks acquiring the bacterium decline. Nothing to do with population size of deer ticks.

D.) There's no mention of deer in the paragraph, just deer ticks. Looks like another trap. Would be more enticing if it mentioned general other species instead of deer specifically.

E.) The author's not concerned with other bacteria, only Lime Disease bacterium. After the first sentence ("Lyme disease is caused by a bacterium transmitted to humans by deer ticks"), each subsequent mention of bacterium is preceded by "the", meaning he is referring to the specific bacterium mentioned in the first sentence. His argument/conclusion is regarding Lyme disease bacterium.

Now.. what's the OA?

I don't know. B?

B...by POE

As I remember,
OA:B

source: GMATPrep
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It 's B because the conclusion is about the dependence of deer stick population on the population of the animals for the tick's larval stage to feed on.