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C for me.
I have used POE to eliminate the wrong answers.
A When a prey insect is moved directly toward a beetle that has been chasing it, the beetle immediately stops and runs away without its usual intermittent stopping. clearly wrong.
B In pursuing a swerving insect, a beetle alters its course while running and its pauses become more frequent as the chase progresses.
gives credence to both the theories.
C In pursuing a moving insect, a beetle usually responds immediately to changes in the insect's direction, and it pauses equally frequently whether the chase is up or down an incline.
This one negates the blind theory and conforms with the pace theory.
D If, when a beetle pauses, it has not gained on the insect it is pursuing, the beetle generally ends its pursuit.
this means that it had to pause first. Second it reevaluated the visual bit and then realized that the insect is very far. Re the pace theory it does not explain why the beetle stopped. so it actually conforms to both the theories.
E The faster a beetle pursues an insect fleeing directly away from it, the more frequently the beetle stops.
again eliminate it.
"a beetle usually responds immediately to changes in the insect's direction" it means beetle doesn't go blind. It undermines the second hypotheses.
"it pauses equally frequently whether the chase is up or down an incline", it means beetle cannot maintain their pace and must pause for a moment's rest. It supports the first hypothese.
You are right about the "a beetle usually responds immediately to changes in the insect's direction", undermining first hypothesis.
I think you are wrong about the second part, "it pauses equally frequently whether the chase is up or down an incline". If the beetle is stopping to catch his breath, then this means the beetle gets equally tired whether running uphill or downhill. How is that possible? Even an athlete gets more tired when running uphill.
In my opinion, B can not be an answer. B says that "In pursuing a swerving insect, a beetle alters its course while running ". It may happen that beetle might be going blind and changing their directions.
That does not make sense, the hypothesis is that the beetle stops when it goes blind. Oh well, lets wait for the official answer I guess.
Re: GMATPREP - CR - Tiger Beetles (what a ripper) [#permalink]
27 May 2008, 17:14
A) When a prey insect is moved directly toward a beetle that has been chasing it, the beetle immediately turns and runs away without its usual intermittent stopping. This sentence suggests a survival issue for Beetle. So whether or not it needs rest or become blind, it has to save its life so keep running. This is not the answer.
B) In pursuing a moving insect, the beetles usually respond immediately to changes in the insect's direction, and pause equally frequently whether the chase is up or down an incline. "usually respond immediately to changes" implies beetle does not become blind so refuting the second hypothesis. "pause equally frequently whether..." implies irrespective of condition they stop, so "rest" is not the issue, as if it is an issue then going up incline they will rest more frequently.
C) The beetles maintain a fixed time interval between pauses, although when an insect that had been stationary begins to flee, the beetle increases its speed after the next pause. "maintain a fixed time interval..." refutes first experiment. "though when an insect..." supports beetle is not able to see it when prey started fleeing, so next time when beetle pauses and see prey is fleeing increases its speed.
D) If, when the beetle pauses, it has not gained on the suspect while pursuing, the beetle generally ends the pursuit. Neither supports the first hypothesis nor the second hypothesis.
E) When an obstacle is suddenly introduced just in front of the running beetles, the beetles stop immediately, but they never respond by running around the barrier. "When an obstacle is.." indicates beetle is not blind thereby refuting second hypothesis but this does not supports the first experiment as required by the question.
So Answer is C.
Last edited by abhijit_sen on 29 May 2008, 05:32, edited 2 times in total.