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标题: 请教prep 29155 [打印本页]

作者: 混乱思维 时间: 2008-8-30 04:52
标题: 请教prep 29155

Tiger beetles are such fast runners that they can capture virtually any nonflying insect. However, when running toward an insect, the beetles intermittently stop, and then, a moment later, resume their attack. Perhaps they cannot maintain their pace and must pause for a moment's rest; but an alternative hypothesis is that while running tiger beetles are unable to process the resulting rapidly changing visual information, and so quickly go blind and stop.

Which of the following, if discovered in experiments using artificially moved prey insects, would support one of the two hypotheses and undermine the other?

(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.

(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.

(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 its next pause.

(D) If, when a beetle pauses, it has not gained on the insect it is pursuing, the beetle generally ends its pursuit.

(E) When an obstacle is suddenly introduced just in front of running beetles, the beetles sometimes stop immediately, but they never respond by running around the barrier.

答案是C,我选的E. beetle increase its speed 跟什么有关呢？需要休息，还是看不见？

作者: dianecarton 时间: 2008-8-30 05:40
The reason C weakens the idea that they have to pause to rest is that presumably, they pause because their strengths have given out. However, C says that they pause at fixed intervals, and if the prey begins to flee, the tiger beetle will increase its speed after the pause. This suggests that it pauses not because it has to rest to recuperate. As it pauses at fixed intervals, and yet can expend more energy by running faster, it means that when the beetle paused before the change in speed, it has not become exhausted. Thus it must have paused for other reasons.

The reason that C strengthens the alternative hypothesis is that the speed of the beetle did not increase the moment the prey begins to flee, but has to wait until the next pause. This suggests that it did not see that the prey has begun to flee until it paused, which supports the idea that the beetle cannot process the changing visual information because it is running so fast.

作者: 混乱思维 时间: 2008-9-16 05:47
lz就是LZ，就是牛，一下子我就明白了。

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