2010年12月英语六级听力练习三十九

Robert knows that healthy, well-watered plants are quiet. He also knows that many insects prefer attacking dry plants rather than healthy plants. How do the insects know which are healthy plants and which are not? Robert thinks that____________________that cry and then they may buzz in to kill.

 To test his theory, Robert is using a device _______________. He attaches it to a quiet, healthy plant so the plant sounds thirsty. Then he watches insects to see if they attack more often than usual.

 If he is right, scientists could use the insects’ ability against them. They could build traps that imitate crying plants. So when____________ , they won’t buzz out.