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 from feeding on infected whitefooted mice. However, certain other species on which the larvae feed do not harbor the bacterium. Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium and hence the number of people contracting Lyme disease—would likely decline.

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

A. Whether populations of the other species on which deer tick larvae feed are found only in areas also inhabited by white footed mice.

B. Whether the size of the deer population is currently limited by the availability of animals for ticks ‘s larval stage to feed on

C. Whether the infected deer 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 transmits to humans.


Was confused between [spoiler]B & D[/spoiler]. Finally chose D. However OA is B.

Can anybody give a clear picture why B?

IMO-D

I also dont understand. To me, B looks out of scope. Would like to see the explanation. Are you sure about the OA?

gmat740 wrote:IMO-D

I also dont understand. To me, B looks out of scope. Would like to see the explanation. Are you sure about the OA?

Sure about the OA. Atleast thats what the GMAT Prep software says!

I guess...we need to attack the assumptions here....

Assumption: increase in uninfected species => low numbers of deer eating these uninfected species => less disease among people....

B questions this assumption correctly....

Will increasing the uninfected species will lead to less number of deer eating these uninfected mice ?

Basically as option B asks.....
if number of deer are limited by amount of food available...
a) Yes:
then even after increasing the uninfected species it will not lead to less number of infected deer....as number of deer too will increase here....WEAKENS
b) No:
then after increasing the unifected species...it will lead to less number of infected deer. STRENGTENS...

IMO since C and D are not talking anything related to assumption...so I guess they are out of scope...

can someone please confirm the reason to kick out C and D please ?