PREP-1-24

GreenGreen

24.   (29155-!-item-!-188;#058&003857)

 

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.

问题：C为什么是对的。怎么排除A,B选项。THANKS!

lanseb8ma

Check the options one by one according to the requirement:

A: both hyptheses are undermined, no rest and no blind stop;

B: undermine the second H, but its support to the first H is inadequate since "the chase up or down an incline" can not be equally demanding to its physical power and thus the pause could not be "equally frequent";

C: undermine the second H and support the first H(the interval, rather than the frequency, could be fixed). 

GreenGreen

lanseb8ma，i  got it.thanks!